Code
P0338
GWM
P — Powertrain
- High reading of crankshaft position sensor A
AI status
Completed
Completed
100%
Causes
- Open or shorted wiring in the crankshaft sensor circuit
- Corroded, damaged, or loose connector(s) at the sensor or ECM
- Failed crankshaft position sensor (Hall-effect or variable-reluctance)
- Incorrect sensor reference voltage (ECM power or reference circuit fault)
- Damaged or missing crankshaft reluctor/tone wheel teeth, debris on reluctor
- Poor ground at ECM or sensor return
Symptoms
- Check Engine Light (MIL) on with P0338 stored
- Hard start or no-start condition
- Intermittent stalling, rough idle or misfire
- Loss of ignition timing or disabled fuel injection in some ECM strategies
- Reduced engine performance or limp mode
What to check
- Read freeze-frame and live data with a scan tool; confirm code and related codes
- Visual inspection of CKP sensor connector, wiring harness, and tone wheel/reluctor
- Check for corrosion, bent pins, crushed wires, or missing connector locks
- Backprobe sensor reference and signal circuits with key ON and during cranking
- Measure sensor resistance (if specified) and compare to factory spec
- Use an oscilloscope to view the sensor waveform while cranking or running
Signal parameters
- Hall-effect CKP (typical): square wave signal referenced to 5 V (0–5 V) with frequency proportional to RPM; reference voltage ~5 V (varies by vehicle).
- Variable-reluctance (VR) CKP (typical): AC sine/alternating waveform; amplitude increases with shaft speed (tens to hundreds of millivolts at cranking to volts at higher RPM).
- Expected idle/crank waveform shape and amplitude vary by sensor type and model — consult GWM service data for exact values.
- With key ON (engine off): Hall sensor reference present; VR sensor shows little/no AC until cranking.
Diagnostic algorithm
- Retrieve all codes and freeze-frame data. Note whether code is current, pending, or historical and any related cam/crank codes.
- Perform a visual inspection: check sensor mounting, tone wheel condition, and harness for chafing, heat damage, or rodent damage.
- Inspect connectors: disconnect the CKP connector, check for corrosion, bent pins, or water intrusion; reconnect firmly.
- Verify reference power and ground: backprobe the connector with key ON. For Hall sensors confirm reference voltage (usually ~5 V) and good ground. Repair as required.
- Check sensor resistance and continuity (if applicable): with ignition OFF, measure resistance between sensor terminals and compare to spec from GWM service data. Replace if out of range.
- Capture live signal: with an oscilloscope or good quality scan tool, observe the CKP signal during cranking and at idle. Look for clean square waves (Hall) or consistent AC waveform (VR).
- Wiggle test: with probe connected, gently move harness and connector to see if signal changes or code returns — helps locate intermittent wiring faults.
- Inspect/repair tone wheel: if waveform missing or irregular, inspect reluctor/tone wheel for damage, missing teeth, or alignment issues.
- Test ECM circuit: if wiring and sensor check OK, verify ECM pin voltages/grounds. Repair wiring or replace ECM module only after eliminating harness and sensor as causes.
- Replace suspect CKP sensor only after verifying wiring and reference circuits are correct. Clear codes and perform a road/crank test to confirm repair.
- Safety note: when probing or cranking, follow safe procedures and keep hands/tools clear of moving parts; disconnect battery if instructed by service manual before high-voltage tests.
Likely causes
- Damaged sensor wiring or connector corrosion
- Failed crankshaft position sensor
- Bad sensor ground or reference voltage fault
- Physical damage or debris on the tone wheel/reluctor
Fault status
Status
Crankshaft Position Sensor A Circuit High Input — ECM detects a voltage/signal above the expected range from the primary crankshaft position sensor circuit.
Repair difficulty: Medium
Diagnostic time: 1.0-3.0 hours
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