Code
P1708
ALFA ROMEO
P — Powertrain
Secondary pressure check fault
Views:
UK: 3
EN: 4
RU: 2
AI status
Completed
Completed
100%
Causes
- Low or contaminated transmission fluid
- External or internal hydraulic leak
- Faulty secondary pressure sensor or pressure switch
- Failed pressure regulator valve or control solenoid
- Clogged transmission filter or passage
- Damaged wiring, poor connector contact or ground to the sensor/solenoid
Symptoms
- Transmission warning light or MIL illuminated
- Transmission enters limp/limitation mode
- Harsh, delayed, or erratic shifting
- Inability to engage certain gears or loss of drive
- Unusual transmission noise or overheating indication
- Possible fluid leak under vehicle
What to check
- Read and record all stored DTCs and freeze‑frame data with a compatible scanner
- Check transmission fluid level and condition (color, smell, contamination) per service manual instructions
- Visually inspect transmission and external hydraulic lines for leaks
- Inspect connectors and wiring to the pressure sensor/switch and solenoids for corrosion, damage or loose pins
- Check for related codes from the TCM (input/output speed sensors, solenoids)
- Confirm vehicle software/TSBs for known issues
Signal parameters
- Secondary (line) hydraulic pressure — actual value (kPa/bar/psi)
- Commanded/target line pressure from TCM
- Pressure sensor/switch status (ON/OFF or voltage)
- Solenoid duty cycle or commanded current for pressure regulation
- Transmission gear selected, engine RPM, vehicle speed
- Transmission fluid temperature
Diagnostic algorithm
- Retrieve and document all codes and freeze‑frame data, then clear codes and recheck to confirm persistence
- Visually inspect transmission fluid level and condition; top up or replace if low or heavily contaminated (follow Alfa Romeo procedure)
- Inspect for external leaks and tighten/replace leaking connectors or hoses
- Check connectors and continuity of wiring to the secondary pressure sensor/switch and related solenoids; repair any damage and ensure a good ground
- Using a scan tool, compare commanded vs actual secondary pressure while performing a controlled test (idle, gear engagement, or on‑road as required)
- If available, attach a calibrated transmission pressure gauge to the secondary pressure port and verify pressure against factory specifications
- Test pressure control solenoid(s) electrically (resistance, activation) and functionally (oscilloscope or scan tool)
- If sensor/switch or solenoid fails tests, replace the faulty component and retest
- If hydraulic pressures remain out of specification after component replacement, inspect internal valve body and pressure regulator for wear/clogging; rebuild or replace as required
- If electrical and hydraulic systems check good, consider TCM diagnosis or reflashing per dealer procedures
Likely causes
- Incorrect transmission fluid level or degraded fluid
- Faulty secondary pressure sensor/switch or its connector
- Sticky or failed pressure regulator valve or control solenoid
- Wiring harness damage or poor ground to transmission components
Fault status
Status
TCM detected abnormal secondary transmission hydraulic pressure during self check — possible low fluid, leak, faulty pressure sensor/switch, solenoid or internal pressure regulator fault.
Repair difficulty: Medium
Diagnostic time: 1.5 - 4.0 hours
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