Code
P0323
Generic
P — Powertrain
Ignition/Distributor Engine Speed Input Circuit Intermittent
AI status
Completed
Completed
100%
Causes
- Damaged or shorted wiring in the crankshaft/ignition speed sensor circuit
- Loose, corroded, or damaged connector at the sensor or ECM
- Faulty crankshaft position (CKP) sensor, hall-effect pickup, or distributor pickup coil
- Contaminated, cracked, or missing reluctor/trigger ring teeth
- Poor sensor or ECM ground or reference voltage issues
- Intermittent internal ECM fault or poor ECM pin contact
Symptoms
- Malfunction Indicator Lamp (MIL) / Check Engine Light illuminated (intermittent)
- Intermittent hard-start, no-start, or stall
- Intermittent misfire, rough idle or hesitation
- RPM gauge jumping or erratic engine speed reading
- Occasional loss of fuel/ignition cut (engine may shut off) when signal is lost
What to check
- Read freeze frame data and stored data with a scan tool; note when the code sets (crank, idle, load, temperature).
- Check for other related DTCs (cam/crank codes, ignition codes) before proceeding.
- Visually inspect sensor, reluctor/trigger ring/distributor for damage, rust, or debris.
- Inspect connectors for corrosion, bent pins, or water intrusion; ensure secure fit.
- Perform wiggle test of wiring and connectors while monitoring live crank/cam signal on a scan tool or oscilloscope.
- Measure sensor supply/reference voltage and ground at the connector with key ON (no crank).
Signal parameters
- Hall-effect (digital) sensors: square wave pulse, typically 0–5 V (logic), frequency proportional to engine speed.
- Inductive/magnetic sensors: AC voltage output that rises with RPM; small AC (~0.2–2 VAC) at cranking up to several volts at higher RPM.
- Reference/supply: many hall sensors use a 5 V reference and a ground — verify ~5 V supply present with key ON.
- Frequency: proportional to engine RPM — at idle the pulse rate is generally in the range of tens to low hundreds of Hz depending on engine design.
Diagnostic algorithm
- Retrieve freeze frame and full data with a scan tool; note conditions when P0323 set (rpm, load, temp).
- Visually inspect sensor, reluctor ring/distributor, wiring harness and connectors for damage, corrosion, or fluid intrusion.
- Backprobe sensor connector. With key ON (engine off) verify reference voltage and ground presence for hall-type sensors.
- Crank engine and monitor sensor waveform with an oscilloscope or live data. Look for missing pulses, noise, amplitude drops or intermittent signal loss.
- Perform a wiggle test of wiring and connectors while observing the live signal—if code or signal changes, repair/replace the affected wiring/connector.
- Check continuity and resistance of the sensor circuit to the ECM; repair any high-resistance or intermittent connections.
- Inspect reluctor/trigger wheel for missing or damaged teeth; repair or replace as needed.
- If wiring and trigger hardware are good but signal is intermittent, replace the sensor (CKP or pickup).
- If symptoms persist after sensor and wiring repairs, inspect ECM connector pins and grounds; consider ECM bench test or replacement only after ruling out harness and sensor faults.
- Clear codes, road test under the same conditions and re-check for reoccurrence. Confirm repair with repeated data checks.
Likely causes
- Broken/loose wire or intermittent connector at CKP sensor
- Worn or damaged reluctor ring or distributor pickup
- Intermittent CKP or pickup sensor failure (temperature/ vibration related)
- Poor ground or intermittent supply/reference voltage to the sensor
Fault status
Status
Intermittent loss or corruption of the ignition/distributor (engine speed) input signal to the ECM. The ECM detects irregular or missing pulses from the crank/ignition pickup.
Repair difficulty: Medium
Diagnostic time: 1-3 hours
Similar codes
Repair manuals
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Code
P0323
GWM
P — Powertrain
- Ignition Switch Circuit Malfunction
AI status
Completed
Completed
100%
Causes
- Damaged or shorted wiring in the crankshaft/ignition speed sensor circuit
- Loose, corroded, or damaged connector at the sensor or ECM
- Faulty crankshaft position (CKP) sensor, hall-effect pickup, or distributor pickup coil
- Contaminated, cracked, or missing reluctor/trigger ring teeth
- Poor sensor or ECM ground or reference voltage issues
- Intermittent internal ECM fault or poor ECM pin contact
Symptoms
- Malfunction Indicator Lamp (MIL) / Check Engine Light illuminated (intermittent)
- Intermittent hard-start, no-start, or stall
- Intermittent misfire, rough idle or hesitation
- RPM gauge jumping or erratic engine speed reading
- Occasional loss of fuel/ignition cut (engine may shut off) when signal is lost
What to check
- Read freeze frame data and stored data with a scan tool; note when the code sets (crank, idle, load, temperature).
- Check for other related DTCs (cam/crank codes, ignition codes) before proceeding.
- Visually inspect sensor, reluctor/trigger ring/distributor for damage, rust, or debris.
- Inspect connectors for corrosion, bent pins, or water intrusion; ensure secure fit.
- Perform wiggle test of wiring and connectors while monitoring live crank/cam signal on a scan tool or oscilloscope.
- Measure sensor supply/reference voltage and ground at the connector with key ON (no crank).
Signal parameters
- Hall-effect (digital) sensors: square wave pulse, typically 0–5 V (logic), frequency proportional to engine speed.
- Inductive/magnetic sensors: AC voltage output that rises with RPM; small AC (~0.2–2 VAC) at cranking up to several volts at higher RPM.
- Reference/supply: many hall sensors use a 5 V reference and a ground — verify ~5 V supply present with key ON.
- Frequency: proportional to engine RPM — at idle the pulse rate is generally in the range of tens to low hundreds of Hz depending on engine design.
Diagnostic algorithm
- Retrieve freeze frame and full data with a scan tool; note conditions when P0323 set (rpm, load, temp).
- Visually inspect sensor, reluctor ring/distributor, wiring harness and connectors for damage, corrosion, or fluid intrusion.
- Backprobe sensor connector. With key ON (engine off) verify reference voltage and ground presence for hall-type sensors.
- Crank engine and monitor sensor waveform with an oscilloscope or live data. Look for missing pulses, noise, amplitude drops or intermittent signal loss.
- Perform a wiggle test of wiring and connectors while observing the live signal—if code or signal changes, repair/replace the affected wiring/connector.
- Check continuity and resistance of the sensor circuit to the ECM; repair any high-resistance or intermittent connections.
- Inspect reluctor/trigger wheel for missing or damaged teeth; repair or replace as needed.
- If wiring and trigger hardware are good but signal is intermittent, replace the sensor (CKP or pickup).
- If symptoms persist after sensor and wiring repairs, inspect ECM connector pins and grounds; consider ECM bench test or replacement only after ruling out harness and sensor faults.
- Clear codes, road test under the same conditions and re-check for reoccurrence. Confirm repair with repeated data checks.
Likely causes
- Broken/loose wire or intermittent connector at CKP sensor
- Worn or damaged reluctor ring or distributor pickup
- Intermittent CKP or pickup sensor failure (temperature/ vibration related)
- Poor ground or intermittent supply/reference voltage to the sensor
Fault status
Status
Intermittent loss or corruption of the ignition/distributor (engine speed) input signal to the ECM. The ECM detects irregular or missing pulses from the crank/ignition pickup.
Repair difficulty: Medium
Diagnostic time: 1-3 hours
Similar codes
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Code
P0323
HUMMER
P — Powertrain
Ignition/Distributor Engine Speed Input Circuit Intermittent
AI status
Completed
Completed
100%
Causes
- Damaged or shorted wiring in the crankshaft/ignition speed sensor circuit
- Loose, corroded, or damaged connector at the sensor or ECM
- Faulty crankshaft position (CKP) sensor, hall-effect pickup, or distributor pickup coil
- Contaminated, cracked, or missing reluctor/trigger ring teeth
- Poor sensor or ECM ground or reference voltage issues
- Intermittent internal ECM fault or poor ECM pin contact
Symptoms
- Malfunction Indicator Lamp (MIL) / Check Engine Light illuminated (intermittent)
- Intermittent hard-start, no-start, or stall
- Intermittent misfire, rough idle or hesitation
- RPM gauge jumping or erratic engine speed reading
- Occasional loss of fuel/ignition cut (engine may shut off) when signal is lost
What to check
- Read freeze frame data and stored data with a scan tool; note when the code sets (crank, idle, load, temperature).
- Check for other related DTCs (cam/crank codes, ignition codes) before proceeding.
- Visually inspect sensor, reluctor/trigger ring/distributor for damage, rust, or debris.
- Inspect connectors for corrosion, bent pins, or water intrusion; ensure secure fit.
- Perform wiggle test of wiring and connectors while monitoring live crank/cam signal on a scan tool or oscilloscope.
- Measure sensor supply/reference voltage and ground at the connector with key ON (no crank).
Signal parameters
- Hall-effect (digital) sensors: square wave pulse, typically 0–5 V (logic), frequency proportional to engine speed.
- Inductive/magnetic sensors: AC voltage output that rises with RPM; small AC (~0.2–2 VAC) at cranking up to several volts at higher RPM.
- Reference/supply: many hall sensors use a 5 V reference and a ground — verify ~5 V supply present with key ON.
- Frequency: proportional to engine RPM — at idle the pulse rate is generally in the range of tens to low hundreds of Hz depending on engine design.
Diagnostic algorithm
- Retrieve freeze frame and full data with a scan tool; note conditions when P0323 set (rpm, load, temp).
- Visually inspect sensor, reluctor ring/distributor, wiring harness and connectors for damage, corrosion, or fluid intrusion.
- Backprobe sensor connector. With key ON (engine off) verify reference voltage and ground presence for hall-type sensors.
- Crank engine and monitor sensor waveform with an oscilloscope or live data. Look for missing pulses, noise, amplitude drops or intermittent signal loss.
- Perform a wiggle test of wiring and connectors while observing the live signal—if code or signal changes, repair/replace the affected wiring/connector.
- Check continuity and resistance of the sensor circuit to the ECM; repair any high-resistance or intermittent connections.
- Inspect reluctor/trigger wheel for missing or damaged teeth; repair or replace as needed.
- If wiring and trigger hardware are good but signal is intermittent, replace the sensor (CKP or pickup).
- If symptoms persist after sensor and wiring repairs, inspect ECM connector pins and grounds; consider ECM bench test or replacement only after ruling out harness and sensor faults.
- Clear codes, road test under the same conditions and re-check for reoccurrence. Confirm repair with repeated data checks.
Likely causes
- Broken/loose wire or intermittent connector at CKP sensor
- Worn or damaged reluctor ring or distributor pickup
- Intermittent CKP or pickup sensor failure (temperature/ vibration related)
- Poor ground or intermittent supply/reference voltage to the sensor
Fault status
Status
Intermittent loss or corruption of the ignition/distributor (engine speed) input signal to the ECM. The ECM detects irregular or missing pulses from the crank/ignition pickup.
Repair difficulty: Medium
Diagnostic time: 1-3 hours
Similar codes
Repair manuals
Manual library for HUMMER
138
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