Code
P0337
GWM
P — Powertrain
- Crankshaft Position Sensor A Low
AI status
Completed
Completed
100%
Causes
- Faulty crankshaft position (CKP) sensor (Hall or VR type)
- Short to ground in CKP sensor signal wire
- Open or high-resistance wiring/connectors between sensor and PCM
- Corroded or loose sensor connector or PCM connector
- Damaged or missing reluctor/trigger wheel teeth (physical damage)
- Excessive sensor air-gap or misalignment
Symptoms
- Check Engine / Malfunction Indicator Lamp illuminated
- Engine may not crank or will crank but fail to start
- Rough idle, misfires, or stalling
- Poor acceleration or reduced engine power
- Intermittent starting or sporadic drivability problems
- Crank/no-start that improves after diagnostics/repairs
What to check
- Read DTCs and freeze-frame data with a scan tool; note engine speed and conditions when the code set
- Attempt to reproduce the fault; determine if code is present at cranking or running
- Visually inspect CKP sensor, connector and wiring for damage, corrosion, or pinched areas
- Back-probe sensor connector to check reference voltage (if Hall-type), signal voltage, and ground with a multimeter
- Measure sensor resistance (for VR sensors check coil resistance per manufacturer spec) and continuity to PCM
- Check for short to ground on the signal wire (pin-to-ground) and short to power (pin-to-B+)
Signal parameters
- Hall-effect sensor: 0–5 V square-wave output (switching between near 0 V and ~5 V); frequency proportional to engine RPM
- VR (variable reluctance) sensor: AC waveform; low AC voltage at cranking (often >0.2 V AC) increasing with RPM (typically several hundred mV to volts depending on engine speed)
- Expected signal presence during cranking; complete absence or pulled-low signal indicates circuit low
- Resistance for VR coils commonly in the low hundreds to a few thousand ohms (manufacturer-specific); Hall sensors have full-range digital switching so resistance check may be not applicable
Diagnostic algorithm
- Verify DTC — read and record P0337 and any related codes (P0335/P0338/P0339/P0340/P0016). Clear codes and attempt to reproduce.
- Visual inspection — check sensor body, mounting, harness routing, connector condition, and reluctor wheel. Repair any obvious damage.
- Check supply & ground — with key on, back-probe connector: confirm sensor reference power (Hall-type), ground, and signal circuit continuity to the PCM.
- Measure sensor output — crank engine while measuring signal: for Hall sensor confirm switching 0–5 V; for VR sensor measure AC voltage. If no signal, suspect sensor/harness/reluctor.
- Wiggle test and continuity checks — wiggle harness and connectors while observing signal or using continuity/ohm meter to identify intermittent opens/shorts.
- Inspect trigger wheel/air-gap — measure/confirm air-gap and look for missing or damaged teeth; correct alignment or replace reluctor if damaged.
- Repair wiring or replace sensor — fix shorts, corrosion, or connector faults. Replace CKP sensor if output/resistance out of spec or waveform abnormal.
- Re-test — clear codes and verify normal operation and that DTC does not return. If fault persists after sensor/wiring repair, consider PCM input circuit testing or replacement (rare).
- If available, use an oscilloscope to compare waveform to known-good pattern for final confirmation.
Likely causes
- Damaged or failed CKP sensor
- Shorted signal wire to ground or pinched harness
- Corroded/loose sensor connector or high resistance at connector
- Damaged or mispositioned reluctor/trigger wheel
- Incorrect sensor air-gap or mechanical interference
Fault status
Status
P0337 stored — Crankshaft Position Sensor A Circuit Low Input. The PCM detected a low or absent signal on the CKP sensor A circuit (signal pulled toward ground or no signal) under monitoring conditions. Possible causes include sensor failure, wiring short to ground, connector/corrosion issues, or damaged trigger wheel.
Repair difficulty: Medium
Diagnostic time: 0.5–2 hours
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