P1704
Autotransmission | Secondary pressure sensor
Causes
- Faulty secondary (line) pressure sensor
- Damaged, corroded or disconnected wiring/connector to the sensor
- Poor sensor ground or lost reference/5V supply from TCM
- Hydraulic issue (blocked/contaminated pressure port, internal valve body leak)
- Faulty TCM (rare) or software/calibration fault
- Incorrect transmission fluid level or severely degraded fluid affecting pressure readings
Symptoms
- MIL (Check Engine/Transmission warning) illuminated
- Harsh, delayed or erratic gear shifts
- Transmission slipping or failing to engage certain gears
- Vehicle may enter limp-home mode with limited gear selection
- Transmission-related fault messages displayed in cluster
- Unusual transmission noise or degraded driveability
What to check
- Read freeze frame and live data with a capable scan tool; note secondary pressure sensor values, related flags, and transmission temperature
- Visual inspection of sensor connector and wiring for corrosion, damage, pin push-out or fluid ingress
- Backprobe sensor connector and measure signal voltage with key ON / engine OFF and while running (observe change with throttle if safe)
- Verify reference supply (usually 5V) and ground integrity at the sensor connector
- Check for shorts to battery or ground using a multimeter and continuity tests
- If available, attach an external transmission pressure gauge to compare hydraulic pressure with sensor readings
Signal parameters
- Typical sensor output: ~0.5–4.5 V proportional to measured pressure (manufacturer-specific curve — consult Alfa Romeo spec)
- Reference supply: 5 V (approx.) from TCM; confirm stable 4.8–5.2 V at connector
- Ground: low resistance (
- Expected dynamic behavior: signal changes smoothly with throttle/gear changes; no rapid spikes or dropouts
- If using an absolute pressure scale: secondary/line pressure may typically range from 0–15 bar depending on gear and throttle (use factory spec for exact values)
Diagnostic algorithm
- Retrieve and record all related DTCs, freeze frame and live data (secondary pressure, primary pressure, transmission temp, speed sensors).
- Visually inspect the secondary pressure sensor, connector and harness for damage, fluid contamination or corrosion. Repair connector issues if found.
- With key ON engine OFF, backprobe the sensor connector: verify presence of reference voltage (≈5 V) and good ground. If absent, trace to TCM.
- Start engine and monitor sensor output voltage; observe whether signal varies smoothly with throttle and gear changes. Check for intermittent behavior while gently moving harness to reproduce fault.
- If electrical supply/ground are good but signal is out of range or erratic, disconnect sensor and measure its output/resistance per factory procedure — replace sensor if out of spec.
- If sensor reads plausible but transmission behavior or pressure does not match, connect a mechanical transmission pressure gauge to the secondary pressure port and compare actual hydraulic pressure to sensor reading.
- If mechanical pressure is correct but sensor/TCM disagrees, suspect sensor or wiring; if mechanical pressure is incorrect, inspect valve body, solenoids and hydraulic circuits for blockage/leak.
- Check for TCM software updates or known technical service bulletins. If all wiring and sensor tests are good and issue persists, consider TCM fault (confirm with bench or swap tests if available).
- After repairs, clear codes and perform a road test while monitoring live data to confirm the fault is resolved.
Likely causes
- Open or short in sensor harness (connector corrosion or broken wire)
- Sensor electrical failure (out-of-range voltage or internal short)
- Contaminated hydraulic port at sensor or internal valve-body problem causing abnormal pressure
- Intermittent ground or supply from TCM causing implausible sensor voltage
Fault status
Similar codes
P1704
Tps -high input
Causes
- Faulty secondary (line) pressure sensor
- Damaged, corroded or disconnected wiring/connector to the sensor
- Poor sensor ground or lost reference/5V supply from TCM
- Hydraulic issue (blocked/contaminated pressure port, internal valve body leak)
- Faulty TCM (rare) or software/calibration fault
- Incorrect transmission fluid level or severely degraded fluid affecting pressure readings
Symptoms
- MIL (Check Engine/Transmission warning) illuminated
- Harsh, delayed or erratic gear shifts
- Transmission slipping or failing to engage certain gears
- Vehicle may enter limp-home mode with limited gear selection
- Transmission-related fault messages displayed in cluster
- Unusual transmission noise or degraded driveability
What to check
- Read freeze frame and live data with a capable scan tool; note secondary pressure sensor values, related flags, and transmission temperature
- Visual inspection of sensor connector and wiring for corrosion, damage, pin push-out or fluid ingress
- Backprobe sensor connector and measure signal voltage with key ON / engine OFF and while running (observe change with throttle if safe)
- Verify reference supply (usually 5V) and ground integrity at the sensor connector
- Check for shorts to battery or ground using a multimeter and continuity tests
- If available, attach an external transmission pressure gauge to compare hydraulic pressure with sensor readings
Signal parameters
- Typical sensor output: ~0.5–4.5 V proportional to measured pressure (manufacturer-specific curve — consult Alfa Romeo spec)
- Reference supply: 5 V (approx.) from TCM; confirm stable 4.8–5.2 V at connector
- Ground: low resistance (
- Expected dynamic behavior: signal changes smoothly with throttle/gear changes; no rapid spikes or dropouts
- If using an absolute pressure scale: secondary/line pressure may typically range from 0–15 bar depending on gear and throttle (use factory spec for exact values)
Diagnostic algorithm
- Retrieve and record all related DTCs, freeze frame and live data (secondary pressure, primary pressure, transmission temp, speed sensors).
- Visually inspect the secondary pressure sensor, connector and harness for damage, fluid contamination or corrosion. Repair connector issues if found.
- With key ON engine OFF, backprobe the sensor connector: verify presence of reference voltage (≈5 V) and good ground. If absent, trace to TCM.
- Start engine and monitor sensor output voltage; observe whether signal varies smoothly with throttle and gear changes. Check for intermittent behavior while gently moving harness to reproduce fault.
- If electrical supply/ground are good but signal is out of range or erratic, disconnect sensor and measure its output/resistance per factory procedure — replace sensor if out of spec.
- If sensor reads plausible but transmission behavior or pressure does not match, connect a mechanical transmission pressure gauge to the secondary pressure port and compare actual hydraulic pressure to sensor reading.
- If mechanical pressure is correct but sensor/TCM disagrees, suspect sensor or wiring; if mechanical pressure is incorrect, inspect valve body, solenoids and hydraulic circuits for blockage/leak.
- Check for TCM software updates or known technical service bulletins. If all wiring and sensor tests are good and issue persists, consider TCM fault (confirm with bench or swap tests if available).
- After repairs, clear codes and perform a road test while monitoring live data to confirm the fault is resolved.
Likely causes
- Open or short in sensor harness (connector corrosion or broken wire)
- Sensor electrical failure (out-of-range voltage or internal short)
- Contaminated hydraulic port at sensor or internal valve-body problem causing abnormal pressure
- Intermittent ground or supply from TCM causing implausible sensor voltage
Fault status
Similar codes
P1704
Shift gear switch circuit short
Causes
- Faulty secondary (line) pressure sensor
- Damaged, corroded or disconnected wiring/connector to the sensor
- Poor sensor ground or lost reference/5V supply from TCM
- Hydraulic issue (blocked/contaminated pressure port, internal valve body leak)
- Faulty TCM (rare) or software/calibration fault
- Incorrect transmission fluid level or severely degraded fluid affecting pressure readings
Symptoms
- MIL (Check Engine/Transmission warning) illuminated
- Harsh, delayed or erratic gear shifts
- Transmission slipping or failing to engage certain gears
- Vehicle may enter limp-home mode with limited gear selection
- Transmission-related fault messages displayed in cluster
- Unusual transmission noise or degraded driveability
What to check
- Read freeze frame and live data with a capable scan tool; note secondary pressure sensor values, related flags, and transmission temperature
- Visual inspection of sensor connector and wiring for corrosion, damage, pin push-out or fluid ingress
- Backprobe sensor connector and measure signal voltage with key ON / engine OFF and while running (observe change with throttle if safe)
- Verify reference supply (usually 5V) and ground integrity at the sensor connector
- Check for shorts to battery or ground using a multimeter and continuity tests
- If available, attach an external transmission pressure gauge to compare hydraulic pressure with sensor readings
Signal parameters
- Typical sensor output: ~0.5–4.5 V proportional to measured pressure (manufacturer-specific curve — consult Alfa Romeo spec)
- Reference supply: 5 V (approx.) from TCM; confirm stable 4.8–5.2 V at connector
- Ground: low resistance (
- Expected dynamic behavior: signal changes smoothly with throttle/gear changes; no rapid spikes or dropouts
- If using an absolute pressure scale: secondary/line pressure may typically range from 0–15 bar depending on gear and throttle (use factory spec for exact values)
Diagnostic algorithm
- Retrieve and record all related DTCs, freeze frame and live data (secondary pressure, primary pressure, transmission temp, speed sensors).
- Visually inspect the secondary pressure sensor, connector and harness for damage, fluid contamination or corrosion. Repair connector issues if found.
- With key ON engine OFF, backprobe the sensor connector: verify presence of reference voltage (≈5 V) and good ground. If absent, trace to TCM.
- Start engine and monitor sensor output voltage; observe whether signal varies smoothly with throttle and gear changes. Check for intermittent behavior while gently moving harness to reproduce fault.
- If electrical supply/ground are good but signal is out of range or erratic, disconnect sensor and measure its output/resistance per factory procedure — replace sensor if out of spec.
- If sensor reads plausible but transmission behavior or pressure does not match, connect a mechanical transmission pressure gauge to the secondary pressure port and compare actual hydraulic pressure to sensor reading.
- If mechanical pressure is correct but sensor/TCM disagrees, suspect sensor or wiring; if mechanical pressure is incorrect, inspect valve body, solenoids and hydraulic circuits for blockage/leak.
- Check for TCM software updates or known technical service bulletins. If all wiring and sensor tests are good and issue persists, consider TCM fault (confirm with bench or swap tests if available).
- After repairs, clear codes and perform a road test while monitoring live data to confirm the fault is resolved.
Likely causes
- Open or short in sensor harness (connector corrosion or broken wire)
- Sensor electrical failure (out-of-range voltage or internal short)
- Contaminated hydraulic port at sensor or internal valve-body problem causing abnormal pressure
- Intermittent ground or supply from TCM causing implausible sensor voltage
Fault status
Similar codes
P1704
Autotransmission | Secondary pressure sensor
Causes
- Faulty secondary (line) pressure sensor
- Damaged, corroded or disconnected wiring/connector to the sensor
- Poor sensor ground or lost reference/5V supply from TCM
- Hydraulic issue (blocked/contaminated pressure port, internal valve body leak)
- Faulty TCM (rare) or software/calibration fault
- Incorrect transmission fluid level or severely degraded fluid affecting pressure readings
Symptoms
- MIL (Check Engine/Transmission warning) illuminated
- Harsh, delayed or erratic gear shifts
- Transmission slipping or failing to engage certain gears
- Vehicle may enter limp-home mode with limited gear selection
- Transmission-related fault messages displayed in cluster
- Unusual transmission noise or degraded driveability
What to check
- Read freeze frame and live data with a capable scan tool; note secondary pressure sensor values, related flags, and transmission temperature
- Visual inspection of sensor connector and wiring for corrosion, damage, pin push-out or fluid ingress
- Backprobe sensor connector and measure signal voltage with key ON / engine OFF and while running (observe change with throttle if safe)
- Verify reference supply (usually 5V) and ground integrity at the sensor connector
- Check for shorts to battery or ground using a multimeter and continuity tests
- If available, attach an external transmission pressure gauge to compare hydraulic pressure with sensor readings
Signal parameters
- Typical sensor output: ~0.5–4.5 V proportional to measured pressure (manufacturer-specific curve — consult Alfa Romeo spec)
- Reference supply: 5 V (approx.) from TCM; confirm stable 4.8–5.2 V at connector
- Ground: low resistance (
- Expected dynamic behavior: signal changes smoothly with throttle/gear changes; no rapid spikes or dropouts
- If using an absolute pressure scale: secondary/line pressure may typically range from 0–15 bar depending on gear and throttle (use factory spec for exact values)
Diagnostic algorithm
- Retrieve and record all related DTCs, freeze frame and live data (secondary pressure, primary pressure, transmission temp, speed sensors).
- Visually inspect the secondary pressure sensor, connector and harness for damage, fluid contamination or corrosion. Repair connector issues if found.
- With key ON engine OFF, backprobe the sensor connector: verify presence of reference voltage (≈5 V) and good ground. If absent, trace to TCM.
- Start engine and monitor sensor output voltage; observe whether signal varies smoothly with throttle and gear changes. Check for intermittent behavior while gently moving harness to reproduce fault.
- If electrical supply/ground are good but signal is out of range or erratic, disconnect sensor and measure its output/resistance per factory procedure — replace sensor if out of spec.
- If sensor reads plausible but transmission behavior or pressure does not match, connect a mechanical transmission pressure gauge to the secondary pressure port and compare actual hydraulic pressure to sensor reading.
- If mechanical pressure is correct but sensor/TCM disagrees, suspect sensor or wiring; if mechanical pressure is incorrect, inspect valve body, solenoids and hydraulic circuits for blockage/leak.
- Check for TCM software updates or known technical service bulletins. If all wiring and sensor tests are good and issue persists, consider TCM fault (confirm with bench or swap tests if available).
- After repairs, clear codes and perform a road test while monitoring live data to confirm the fault is resolved.
Likely causes
- Open or short in sensor harness (connector corrosion or broken wire)
- Sensor electrical failure (out-of-range voltage or internal short)
- Contaminated hydraulic port at sensor or internal valve-body problem causing abnormal pressure
- Intermittent ground or supply from TCM causing implausible sensor voltage
Fault status
Similar codes
P1704
Transmission system problems
Causes
- Faulty secondary (line) pressure sensor
- Damaged, corroded or disconnected wiring/connector to the sensor
- Poor sensor ground or lost reference/5V supply from TCM
- Hydraulic issue (blocked/contaminated pressure port, internal valve body leak)
- Faulty TCM (rare) or software/calibration fault
- Incorrect transmission fluid level or severely degraded fluid affecting pressure readings
Symptoms
- MIL (Check Engine/Transmission warning) illuminated
- Harsh, delayed or erratic gear shifts
- Transmission slipping or failing to engage certain gears
- Vehicle may enter limp-home mode with limited gear selection
- Transmission-related fault messages displayed in cluster
- Unusual transmission noise or degraded driveability
What to check
- Read freeze frame and live data with a capable scan tool; note secondary pressure sensor values, related flags, and transmission temperature
- Visual inspection of sensor connector and wiring for corrosion, damage, pin push-out or fluid ingress
- Backprobe sensor connector and measure signal voltage with key ON / engine OFF and while running (observe change with throttle if safe)
- Verify reference supply (usually 5V) and ground integrity at the sensor connector
- Check for shorts to battery or ground using a multimeter and continuity tests
- If available, attach an external transmission pressure gauge to compare hydraulic pressure with sensor readings
Signal parameters
- Typical sensor output: ~0.5–4.5 V proportional to measured pressure (manufacturer-specific curve — consult Alfa Romeo spec)
- Reference supply: 5 V (approx.) from TCM; confirm stable 4.8–5.2 V at connector
- Ground: low resistance (
- Expected dynamic behavior: signal changes smoothly with throttle/gear changes; no rapid spikes or dropouts
- If using an absolute pressure scale: secondary/line pressure may typically range from 0–15 bar depending on gear and throttle (use factory spec for exact values)
Diagnostic algorithm
- Retrieve and record all related DTCs, freeze frame and live data (secondary pressure, primary pressure, transmission temp, speed sensors).
- Visually inspect the secondary pressure sensor, connector and harness for damage, fluid contamination or corrosion. Repair connector issues if found.
- With key ON engine OFF, backprobe the sensor connector: verify presence of reference voltage (≈5 V) and good ground. If absent, trace to TCM.
- Start engine and monitor sensor output voltage; observe whether signal varies smoothly with throttle and gear changes. Check for intermittent behavior while gently moving harness to reproduce fault.
- If electrical supply/ground are good but signal is out of range or erratic, disconnect sensor and measure its output/resistance per factory procedure — replace sensor if out of spec.
- If sensor reads plausible but transmission behavior or pressure does not match, connect a mechanical transmission pressure gauge to the secondary pressure port and compare actual hydraulic pressure to sensor reading.
- If mechanical pressure is correct but sensor/TCM disagrees, suspect sensor or wiring; if mechanical pressure is incorrect, inspect valve body, solenoids and hydraulic circuits for blockage/leak.
- Check for TCM software updates or known technical service bulletins. If all wiring and sensor tests are good and issue persists, consider TCM fault (confirm with bench or swap tests if available).
- After repairs, clear codes and perform a road test while monitoring live data to confirm the fault is resolved.
Likely causes
- Open or short in sensor harness (connector corrosion or broken wire)
- Sensor electrical failure (out-of-range voltage or internal short)
- Contaminated hydraulic port at sensor or internal valve-body problem causing abnormal pressure
- Intermittent ground or supply from TCM causing implausible sensor voltage
Fault status
Similar codes
P1704
Rotary switch failed to transition state
Causes
- Faulty secondary (line) pressure sensor
- Damaged, corroded or disconnected wiring/connector to the sensor
- Poor sensor ground or lost reference/5V supply from TCM
- Hydraulic issue (blocked/contaminated pressure port, internal valve body leak)
- Faulty TCM (rare) or software/calibration fault
- Incorrect transmission fluid level or severely degraded fluid affecting pressure readings
Symptoms
- MIL (Check Engine/Transmission warning) illuminated
- Harsh, delayed or erratic gear shifts
- Transmission slipping or failing to engage certain gears
- Vehicle may enter limp-home mode with limited gear selection
- Transmission-related fault messages displayed in cluster
- Unusual transmission noise or degraded driveability
What to check
- Read freeze frame and live data with a capable scan tool; note secondary pressure sensor values, related flags, and transmission temperature
- Visual inspection of sensor connector and wiring for corrosion, damage, pin push-out or fluid ingress
- Backprobe sensor connector and measure signal voltage with key ON / engine OFF and while running (observe change with throttle if safe)
- Verify reference supply (usually 5V) and ground integrity at the sensor connector
- Check for shorts to battery or ground using a multimeter and continuity tests
- If available, attach an external transmission pressure gauge to compare hydraulic pressure with sensor readings
Signal parameters
- Typical sensor output: ~0.5–4.5 V proportional to measured pressure (manufacturer-specific curve — consult Alfa Romeo spec)
- Reference supply: 5 V (approx.) from TCM; confirm stable 4.8–5.2 V at connector
- Ground: low resistance (
- Expected dynamic behavior: signal changes smoothly with throttle/gear changes; no rapid spikes or dropouts
- If using an absolute pressure scale: secondary/line pressure may typically range from 0–15 bar depending on gear and throttle (use factory spec for exact values)
Diagnostic algorithm
- Retrieve and record all related DTCs, freeze frame and live data (secondary pressure, primary pressure, transmission temp, speed sensors).
- Visually inspect the secondary pressure sensor, connector and harness for damage, fluid contamination or corrosion. Repair connector issues if found.
- With key ON engine OFF, backprobe the sensor connector: verify presence of reference voltage (≈5 V) and good ground. If absent, trace to TCM.
- Start engine and monitor sensor output voltage; observe whether signal varies smoothly with throttle and gear changes. Check for intermittent behavior while gently moving harness to reproduce fault.
- If electrical supply/ground are good but signal is out of range or erratic, disconnect sensor and measure its output/resistance per factory procedure — replace sensor if out of spec.
- If sensor reads plausible but transmission behavior or pressure does not match, connect a mechanical transmission pressure gauge to the secondary pressure port and compare actual hydraulic pressure to sensor reading.
- If mechanical pressure is correct but sensor/TCM disagrees, suspect sensor or wiring; if mechanical pressure is incorrect, inspect valve body, solenoids and hydraulic circuits for blockage/leak.
- Check for TCM software updates or known technical service bulletins. If all wiring and sensor tests are good and issue persists, consider TCM fault (confirm with bench or swap tests if available).
- After repairs, clear codes and perform a road test while monitoring live data to confirm the fault is resolved.
Likely causes
- Open or short in sensor harness (connector corrosion or broken wire)
- Sensor electrical failure (out-of-range voltage or internal short)
- Contaminated hydraulic port at sensor or internal valve-body problem causing abnormal pressure
- Intermittent ground or supply from TCM causing implausible sensor voltage
Fault status
Similar codes
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Workshop ManualP1704
Transmission System Problems
Causes
- Faulty secondary (line) pressure sensor
- Damaged, corroded or disconnected wiring/connector to the sensor
- Poor sensor ground or lost reference/5V supply from TCM
- Hydraulic issue (blocked/contaminated pressure port, internal valve body leak)
- Faulty TCM (rare) or software/calibration fault
- Incorrect transmission fluid level or severely degraded fluid affecting pressure readings
Symptoms
- MIL (Check Engine/Transmission warning) illuminated
- Harsh, delayed or erratic gear shifts
- Transmission slipping or failing to engage certain gears
- Vehicle may enter limp-home mode with limited gear selection
- Transmission-related fault messages displayed in cluster
- Unusual transmission noise or degraded driveability
What to check
- Read freeze frame and live data with a capable scan tool; note secondary pressure sensor values, related flags, and transmission temperature
- Visual inspection of sensor connector and wiring for corrosion, damage, pin push-out or fluid ingress
- Backprobe sensor connector and measure signal voltage with key ON / engine OFF and while running (observe change with throttle if safe)
- Verify reference supply (usually 5V) and ground integrity at the sensor connector
- Check for shorts to battery or ground using a multimeter and continuity tests
- If available, attach an external transmission pressure gauge to compare hydraulic pressure with sensor readings
Signal parameters
- Typical sensor output: ~0.5–4.5 V proportional to measured pressure (manufacturer-specific curve — consult Alfa Romeo spec)
- Reference supply: 5 V (approx.) from TCM; confirm stable 4.8–5.2 V at connector
- Ground: low resistance (
- Expected dynamic behavior: signal changes smoothly with throttle/gear changes; no rapid spikes or dropouts
- If using an absolute pressure scale: secondary/line pressure may typically range from 0–15 bar depending on gear and throttle (use factory spec for exact values)
Diagnostic algorithm
- Retrieve and record all related DTCs, freeze frame and live data (secondary pressure, primary pressure, transmission temp, speed sensors).
- Visually inspect the secondary pressure sensor, connector and harness for damage, fluid contamination or corrosion. Repair connector issues if found.
- With key ON engine OFF, backprobe the sensor connector: verify presence of reference voltage (≈5 V) and good ground. If absent, trace to TCM.
- Start engine and monitor sensor output voltage; observe whether signal varies smoothly with throttle and gear changes. Check for intermittent behavior while gently moving harness to reproduce fault.
- If electrical supply/ground are good but signal is out of range or erratic, disconnect sensor and measure its output/resistance per factory procedure — replace sensor if out of spec.
- If sensor reads plausible but transmission behavior or pressure does not match, connect a mechanical transmission pressure gauge to the secondary pressure port and compare actual hydraulic pressure to sensor reading.
- If mechanical pressure is correct but sensor/TCM disagrees, suspect sensor or wiring; if mechanical pressure is incorrect, inspect valve body, solenoids and hydraulic circuits for blockage/leak.
- Check for TCM software updates or known technical service bulletins. If all wiring and sensor tests are good and issue persists, consider TCM fault (confirm with bench or swap tests if available).
- After repairs, clear codes and perform a road test while monitoring live data to confirm the fault is resolved.
Likely causes
- Open or short in sensor harness (connector corrosion or broken wire)
- Sensor electrical failure (out-of-range voltage or internal short)
- Contaminated hydraulic port at sensor or internal valve-body problem causing abnormal pressure
- Intermittent ground or supply from TCM causing implausible sensor voltage
Fault status
Similar codes
P1704
Transmission system problems
Causes
- Faulty secondary (line) pressure sensor
- Damaged, corroded or disconnected wiring/connector to the sensor
- Poor sensor ground or lost reference/5V supply from TCM
- Hydraulic issue (blocked/contaminated pressure port, internal valve body leak)
- Faulty TCM (rare) or software/calibration fault
- Incorrect transmission fluid level or severely degraded fluid affecting pressure readings
Symptoms
- MIL (Check Engine/Transmission warning) illuminated
- Harsh, delayed or erratic gear shifts
- Transmission slipping or failing to engage certain gears
- Vehicle may enter limp-home mode with limited gear selection
- Transmission-related fault messages displayed in cluster
- Unusual transmission noise or degraded driveability
What to check
- Read freeze frame and live data with a capable scan tool; note secondary pressure sensor values, related flags, and transmission temperature
- Visual inspection of sensor connector and wiring for corrosion, damage, pin push-out or fluid ingress
- Backprobe sensor connector and measure signal voltage with key ON / engine OFF and while running (observe change with throttle if safe)
- Verify reference supply (usually 5V) and ground integrity at the sensor connector
- Check for shorts to battery or ground using a multimeter and continuity tests
- If available, attach an external transmission pressure gauge to compare hydraulic pressure with sensor readings
Signal parameters
- Typical sensor output: ~0.5–4.5 V proportional to measured pressure (manufacturer-specific curve — consult Alfa Romeo spec)
- Reference supply: 5 V (approx.) from TCM; confirm stable 4.8–5.2 V at connector
- Ground: low resistance (
- Expected dynamic behavior: signal changes smoothly with throttle/gear changes; no rapid spikes or dropouts
- If using an absolute pressure scale: secondary/line pressure may typically range from 0–15 bar depending on gear and throttle (use factory spec for exact values)
Diagnostic algorithm
- Retrieve and record all related DTCs, freeze frame and live data (secondary pressure, primary pressure, transmission temp, speed sensors).
- Visually inspect the secondary pressure sensor, connector and harness for damage, fluid contamination or corrosion. Repair connector issues if found.
- With key ON engine OFF, backprobe the sensor connector: verify presence of reference voltage (≈5 V) and good ground. If absent, trace to TCM.
- Start engine and monitor sensor output voltage; observe whether signal varies smoothly with throttle and gear changes. Check for intermittent behavior while gently moving harness to reproduce fault.
- If electrical supply/ground are good but signal is out of range or erratic, disconnect sensor and measure its output/resistance per factory procedure — replace sensor if out of spec.
- If sensor reads plausible but transmission behavior or pressure does not match, connect a mechanical transmission pressure gauge to the secondary pressure port and compare actual hydraulic pressure to sensor reading.
- If mechanical pressure is correct but sensor/TCM disagrees, suspect sensor or wiring; if mechanical pressure is incorrect, inspect valve body, solenoids and hydraulic circuits for blockage/leak.
- Check for TCM software updates or known technical service bulletins. If all wiring and sensor tests are good and issue persists, consider TCM fault (confirm with bench or swap tests if available).
- After repairs, clear codes and perform a road test while monitoring live data to confirm the fault is resolved.
Likely causes
- Open or short in sensor harness (connector corrosion or broken wire)
- Sensor electrical failure (out-of-range voltage or internal short)
- Contaminated hydraulic port at sensor or internal valve-body problem causing abnormal pressure
- Intermittent ground or supply from TCM causing implausible sensor voltage
Fault status
Similar codes
P1704
Digital TRS Failed to Transition States in KOEO / KOER
Causes
- Faulty secondary (line) pressure sensor
- Damaged, corroded or disconnected wiring/connector to the sensor
- Poor sensor ground or lost reference/5V supply from TCM
- Hydraulic issue (blocked/contaminated pressure port, internal valve body leak)
- Faulty TCM (rare) or software/calibration fault
- Incorrect transmission fluid level or severely degraded fluid affecting pressure readings
Symptoms
- MIL (Check Engine/Transmission warning) illuminated
- Harsh, delayed or erratic gear shifts
- Transmission slipping or failing to engage certain gears
- Vehicle may enter limp-home mode with limited gear selection
- Transmission-related fault messages displayed in cluster
- Unusual transmission noise or degraded driveability
What to check
- Read freeze frame and live data with a capable scan tool; note secondary pressure sensor values, related flags, and transmission temperature
- Visual inspection of sensor connector and wiring for corrosion, damage, pin push-out or fluid ingress
- Backprobe sensor connector and measure signal voltage with key ON / engine OFF and while running (observe change with throttle if safe)
- Verify reference supply (usually 5V) and ground integrity at the sensor connector
- Check for shorts to battery or ground using a multimeter and continuity tests
- If available, attach an external transmission pressure gauge to compare hydraulic pressure with sensor readings
Signal parameters
- Typical sensor output: ~0.5–4.5 V proportional to measured pressure (manufacturer-specific curve — consult Alfa Romeo spec)
- Reference supply: 5 V (approx.) from TCM; confirm stable 4.8–5.2 V at connector
- Ground: low resistance (
- Expected dynamic behavior: signal changes smoothly with throttle/gear changes; no rapid spikes or dropouts
- If using an absolute pressure scale: secondary/line pressure may typically range from 0–15 bar depending on gear and throttle (use factory spec for exact values)
Diagnostic algorithm
- Retrieve and record all related DTCs, freeze frame and live data (secondary pressure, primary pressure, transmission temp, speed sensors).
- Visually inspect the secondary pressure sensor, connector and harness for damage, fluid contamination or corrosion. Repair connector issues if found.
- With key ON engine OFF, backprobe the sensor connector: verify presence of reference voltage (≈5 V) and good ground. If absent, trace to TCM.
- Start engine and monitor sensor output voltage; observe whether signal varies smoothly with throttle and gear changes. Check for intermittent behavior while gently moving harness to reproduce fault.
- If electrical supply/ground are good but signal is out of range or erratic, disconnect sensor and measure its output/resistance per factory procedure — replace sensor if out of spec.
- If sensor reads plausible but transmission behavior or pressure does not match, connect a mechanical transmission pressure gauge to the secondary pressure port and compare actual hydraulic pressure to sensor reading.
- If mechanical pressure is correct but sensor/TCM disagrees, suspect sensor or wiring; if mechanical pressure is incorrect, inspect valve body, solenoids and hydraulic circuits for blockage/leak.
- Check for TCM software updates or known technical service bulletins. If all wiring and sensor tests are good and issue persists, consider TCM fault (confirm with bench or swap tests if available).
- After repairs, clear codes and perform a road test while monitoring live data to confirm the fault is resolved.
Likely causes
- Open or short in sensor harness (connector corrosion or broken wire)
- Sensor electrical failure (out-of-range voltage or internal short)
- Contaminated hydraulic port at sensor or internal valve-body problem causing abnormal pressure
- Intermittent ground or supply from TCM causing implausible sensor voltage
Fault status
Similar codes
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Workshop ManualP1704
Kick-down switch - short to ground
Causes
- Faulty secondary (line) pressure sensor
- Damaged, corroded or disconnected wiring/connector to the sensor
- Poor sensor ground or lost reference/5V supply from TCM
- Hydraulic issue (blocked/contaminated pressure port, internal valve body leak)
- Faulty TCM (rare) or software/calibration fault
- Incorrect transmission fluid level or severely degraded fluid affecting pressure readings
Symptoms
- MIL (Check Engine/Transmission warning) illuminated
- Harsh, delayed or erratic gear shifts
- Transmission slipping or failing to engage certain gears
- Vehicle may enter limp-home mode with limited gear selection
- Transmission-related fault messages displayed in cluster
- Unusual transmission noise or degraded driveability
What to check
- Read freeze frame and live data with a capable scan tool; note secondary pressure sensor values, related flags, and transmission temperature
- Visual inspection of sensor connector and wiring for corrosion, damage, pin push-out or fluid ingress
- Backprobe sensor connector and measure signal voltage with key ON / engine OFF and while running (observe change with throttle if safe)
- Verify reference supply (usually 5V) and ground integrity at the sensor connector
- Check for shorts to battery or ground using a multimeter and continuity tests
- If available, attach an external transmission pressure gauge to compare hydraulic pressure with sensor readings
Signal parameters
- Typical sensor output: ~0.5–4.5 V proportional to measured pressure (manufacturer-specific curve — consult Alfa Romeo spec)
- Reference supply: 5 V (approx.) from TCM; confirm stable 4.8–5.2 V at connector
- Ground: low resistance (
- Expected dynamic behavior: signal changes smoothly with throttle/gear changes; no rapid spikes or dropouts
- If using an absolute pressure scale: secondary/line pressure may typically range from 0–15 bar depending on gear and throttle (use factory spec for exact values)
Diagnostic algorithm
- Retrieve and record all related DTCs, freeze frame and live data (secondary pressure, primary pressure, transmission temp, speed sensors).
- Visually inspect the secondary pressure sensor, connector and harness for damage, fluid contamination or corrosion. Repair connector issues if found.
- With key ON engine OFF, backprobe the sensor connector: verify presence of reference voltage (≈5 V) and good ground. If absent, trace to TCM.
- Start engine and monitor sensor output voltage; observe whether signal varies smoothly with throttle and gear changes. Check for intermittent behavior while gently moving harness to reproduce fault.
- If electrical supply/ground are good but signal is out of range or erratic, disconnect sensor and measure its output/resistance per factory procedure — replace sensor if out of spec.
- If sensor reads plausible but transmission behavior or pressure does not match, connect a mechanical transmission pressure gauge to the secondary pressure port and compare actual hydraulic pressure to sensor reading.
- If mechanical pressure is correct but sensor/TCM disagrees, suspect sensor or wiring; if mechanical pressure is incorrect, inspect valve body, solenoids and hydraulic circuits for blockage/leak.
- Check for TCM software updates or known technical service bulletins. If all wiring and sensor tests are good and issue persists, consider TCM fault (confirm with bench or swap tests if available).
- After repairs, clear codes and perform a road test while monitoring live data to confirm the fault is resolved.
Likely causes
- Open or short in sensor harness (connector corrosion or broken wire)
- Sensor electrical failure (out-of-range voltage or internal short)
- Contaminated hydraulic port at sensor or internal valve-body problem causing abnormal pressure
- Intermittent ground or supply from TCM causing implausible sensor voltage
Fault status
Similar codes
P1704
2-4 Brake Timing Solenoid Valve Circuit Malfunction
Causes
- Faulty secondary (line) pressure sensor
- Damaged, corroded or disconnected wiring/connector to the sensor
- Poor sensor ground or lost reference/5V supply from TCM
- Hydraulic issue (blocked/contaminated pressure port, internal valve body leak)
- Faulty TCM (rare) or software/calibration fault
- Incorrect transmission fluid level or severely degraded fluid affecting pressure readings
Symptoms
- MIL (Check Engine/Transmission warning) illuminated
- Harsh, delayed or erratic gear shifts
- Transmission slipping or failing to engage certain gears
- Vehicle may enter limp-home mode with limited gear selection
- Transmission-related fault messages displayed in cluster
- Unusual transmission noise or degraded driveability
What to check
- Read freeze frame and live data with a capable scan tool; note secondary pressure sensor values, related flags, and transmission temperature
- Visual inspection of sensor connector and wiring for corrosion, damage, pin push-out or fluid ingress
- Backprobe sensor connector and measure signal voltage with key ON / engine OFF and while running (observe change with throttle if safe)
- Verify reference supply (usually 5V) and ground integrity at the sensor connector
- Check for shorts to battery or ground using a multimeter and continuity tests
- If available, attach an external transmission pressure gauge to compare hydraulic pressure with sensor readings
Signal parameters
- Typical sensor output: ~0.5–4.5 V proportional to measured pressure (manufacturer-specific curve — consult Alfa Romeo spec)
- Reference supply: 5 V (approx.) from TCM; confirm stable 4.8–5.2 V at connector
- Ground: low resistance (
- Expected dynamic behavior: signal changes smoothly with throttle/gear changes; no rapid spikes or dropouts
- If using an absolute pressure scale: secondary/line pressure may typically range from 0–15 bar depending on gear and throttle (use factory spec for exact values)
Diagnostic algorithm
- Retrieve and record all related DTCs, freeze frame and live data (secondary pressure, primary pressure, transmission temp, speed sensors).
- Visually inspect the secondary pressure sensor, connector and harness for damage, fluid contamination or corrosion. Repair connector issues if found.
- With key ON engine OFF, backprobe the sensor connector: verify presence of reference voltage (≈5 V) and good ground. If absent, trace to TCM.
- Start engine and monitor sensor output voltage; observe whether signal varies smoothly with throttle and gear changes. Check for intermittent behavior while gently moving harness to reproduce fault.
- If electrical supply/ground are good but signal is out of range or erratic, disconnect sensor and measure its output/resistance per factory procedure — replace sensor if out of spec.
- If sensor reads plausible but transmission behavior or pressure does not match, connect a mechanical transmission pressure gauge to the secondary pressure port and compare actual hydraulic pressure to sensor reading.
- If mechanical pressure is correct but sensor/TCM disagrees, suspect sensor or wiring; if mechanical pressure is incorrect, inspect valve body, solenoids and hydraulic circuits for blockage/leak.
- Check for TCM software updates or known technical service bulletins. If all wiring and sensor tests are good and issue persists, consider TCM fault (confirm with bench or swap tests if available).
- After repairs, clear codes and perform a road test while monitoring live data to confirm the fault is resolved.
Likely causes
- Open or short in sensor harness (connector corrosion or broken wire)
- Sensor electrical failure (out-of-range voltage or internal short)
- Contaminated hydraulic port at sensor or internal valve-body problem causing abnormal pressure
- Intermittent ground or supply from TCM causing implausible sensor voltage
Fault status
Similar codes
P1704
Kick Down Switch Malfunction
Causes
- Faulty secondary (line) pressure sensor
- Damaged, corroded or disconnected wiring/connector to the sensor
- Poor sensor ground or lost reference/5V supply from TCM
- Hydraulic issue (blocked/contaminated pressure port, internal valve body leak)
- Faulty TCM (rare) or software/calibration fault
- Incorrect transmission fluid level or severely degraded fluid affecting pressure readings
Symptoms
- MIL (Check Engine/Transmission warning) illuminated
- Harsh, delayed or erratic gear shifts
- Transmission slipping or failing to engage certain gears
- Vehicle may enter limp-home mode with limited gear selection
- Transmission-related fault messages displayed in cluster
- Unusual transmission noise or degraded driveability
What to check
- Read freeze frame and live data with a capable scan tool; note secondary pressure sensor values, related flags, and transmission temperature
- Visual inspection of sensor connector and wiring for corrosion, damage, pin push-out or fluid ingress
- Backprobe sensor connector and measure signal voltage with key ON / engine OFF and while running (observe change with throttle if safe)
- Verify reference supply (usually 5V) and ground integrity at the sensor connector
- Check for shorts to battery or ground using a multimeter and continuity tests
- If available, attach an external transmission pressure gauge to compare hydraulic pressure with sensor readings
Signal parameters
- Typical sensor output: ~0.5–4.5 V proportional to measured pressure (manufacturer-specific curve — consult Alfa Romeo spec)
- Reference supply: 5 V (approx.) from TCM; confirm stable 4.8–5.2 V at connector
- Ground: low resistance (
- Expected dynamic behavior: signal changes smoothly with throttle/gear changes; no rapid spikes or dropouts
- If using an absolute pressure scale: secondary/line pressure may typically range from 0–15 bar depending on gear and throttle (use factory spec for exact values)
Diagnostic algorithm
- Retrieve and record all related DTCs, freeze frame and live data (secondary pressure, primary pressure, transmission temp, speed sensors).
- Visually inspect the secondary pressure sensor, connector and harness for damage, fluid contamination or corrosion. Repair connector issues if found.
- With key ON engine OFF, backprobe the sensor connector: verify presence of reference voltage (≈5 V) and good ground. If absent, trace to TCM.
- Start engine and monitor sensor output voltage; observe whether signal varies smoothly with throttle and gear changes. Check for intermittent behavior while gently moving harness to reproduce fault.
- If electrical supply/ground are good but signal is out of range or erratic, disconnect sensor and measure its output/resistance per factory procedure — replace sensor if out of spec.
- If sensor reads plausible but transmission behavior or pressure does not match, connect a mechanical transmission pressure gauge to the secondary pressure port and compare actual hydraulic pressure to sensor reading.
- If mechanical pressure is correct but sensor/TCM disagrees, suspect sensor or wiring; if mechanical pressure is incorrect, inspect valve body, solenoids and hydraulic circuits for blockage/leak.
- Check for TCM software updates or known technical service bulletins. If all wiring and sensor tests are good and issue persists, consider TCM fault (confirm with bench or swap tests if available).
- After repairs, clear codes and perform a road test while monitoring live data to confirm the fault is resolved.
Likely causes
- Open or short in sensor harness (connector corrosion or broken wire)
- Sensor electrical failure (out-of-range voltage or internal short)
- Contaminated hydraulic port at sensor or internal valve-body problem causing abnormal pressure
- Intermittent ground or supply from TCM causing implausible sensor voltage
