Code
P0372
Generic
P — Powertrain
Timing Reference High Resolution Signal A Too Few Pulses
AI status
Completed
Completed
100%
Causes
- Faulty camshaft position (high-resolution) sensor
- Damaged or missing teeth on reluctor/tone wheel (cam or timing component)
- Wiring open/corroded/shorted or poor connector connection to the sensor
- Oil, debris or metal shavings fouling the sensor or reluctor wheel
- Timing chain/belt jumped or incorrect cam/crank mechanical timing
- Intermittent supply/ground or reference signal to the sensor
Symptoms
- Check Engine Light (MIL) illuminated and code P0372 stored
- Hard or no start, intermittent stalling or fails to start
- Rough idle, misfires or poor running under load
- Reduced engine performance or limp‑in mode
- Inaccurate ignition timing or advance behavior
- Possible multiple cam/crank correlation codes present
What to check
- Read freeze frame data and stored history for conditions when code set (RPM, load, temperature)
- Scan for other related codes (cam/crank correlation, cam/crank sensor faults)
- Visually inspect cam sensor, connector and wiring for damage, oil or corrosion
- Inspect reluctor/tone wheel for missing/damaged teeth, debris or loose mounting
- Check mechanical cam/crank timing (timing belt/chain condition and alignment marks)
- Backprobe sensor connector and verify reference voltage, ground and signal while cranking/ running
Signal parameters
- Expected behavior: continuous stream of pulses on the high‑resolution cam signal while cranking and running; pulses correlate to cam rotation
- Hall/logic style sensors: square wave ~0–5 V (or sensor supply dependent) with clean transitions
- Variable reluctance (VR) style sensors: AC waveform amplitude rises with RPM (may appear sine‑like); expected amplitude depends on sensor/design
- Pulse count/frequency: proportional to engine speed; the PCM expects a specific number of pulses per cam revolution — too few pulses (gaps or missing pulses) triggers the code
- Typical fault indicators on scope: missing pulses, long gaps, distorted/low amplitude signal, noisy or floating baseline
Diagnostic algorithm
- Confirm the code and capture freeze‑frame data. Clear codes and attempt to reproduce under the same conditions.
- Inspect sensor area: remove debris/oil and check reluctor/tone wheel for damage or looseness.
- Visually inspect wiring harness and connector; repair/clean as needed. Check for rodent damage, pin corrosion or pushed‑out terminals.
- Measure sensor supply voltage and ground at the connector with key ON; compare to specification (typically 5 V or switched supply for hall sensors).
- Backprobe the signal lead while cranking and capture with an oscilloscope. Verify pulse pattern, amplitude and count. Identify whether pulses are missing or intermittent.
- If pulses are missing, wiggle the harness and connectors while monitoring the signal to reproduce the fault; this helps find intermittent wiring faults.
- If waveform is weak or absent, test sensor resistance (for VR) and compare to spec, or substitute a known‑good sensor if available.
- Verify mechanical timing: confirm cam/crank timing marks and check for a jumped timing belt/chain or worn tensioners that would change pulse pattern.
- If wiring and sensor check good and timing is correct, inspect PCM grounds and power distribution. Consider PCM input circuit fault if all else checks good.
- After repairs, clear codes and road test under same conditions to confirm the fault does not return. Re‑scan for related codes and perform final scope comparison.
Likely causes
- High‑resolution cam position sensor failed or intermittent
- Reluctor/tone wheel physical damage, missing teeth or loose mounting
- Connector corrosion, pinbacking or chafed wiring causing intermittent signal loss
- Timing chain/belt jumped/failed causing loss of expected pulse pattern
Fault status
Status
PCM detected fewer than the expected high‑resolution timing pulses on Timing Reference A input; timing reference signal is incomplete or intermittent.
Repair difficulty: Medium
Diagnostic time: 0.5-3 hours
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Code
P0372
GWM
P — Powertrain
- The number of pulses of the timer signal A is below the norm
AI status
Completed
Completed
100%
Causes
- Faulty camshaft position (high-resolution) sensor
- Damaged or missing teeth on reluctor/tone wheel (cam or timing component)
- Wiring open/corroded/shorted or poor connector connection to the sensor
- Oil, debris or metal shavings fouling the sensor or reluctor wheel
- Timing chain/belt jumped or incorrect cam/crank mechanical timing
- Intermittent supply/ground or reference signal to the sensor
Symptoms
- Check Engine Light (MIL) illuminated and code P0372 stored
- Hard or no start, intermittent stalling or fails to start
- Rough idle, misfires or poor running under load
- Reduced engine performance or limp‑in mode
- Inaccurate ignition timing or advance behavior
- Possible multiple cam/crank correlation codes present
What to check
- Read freeze frame data and stored history for conditions when code set (RPM, load, temperature)
- Scan for other related codes (cam/crank correlation, cam/crank sensor faults)
- Visually inspect cam sensor, connector and wiring for damage, oil or corrosion
- Inspect reluctor/tone wheel for missing/damaged teeth, debris or loose mounting
- Check mechanical cam/crank timing (timing belt/chain condition and alignment marks)
- Backprobe sensor connector and verify reference voltage, ground and signal while cranking/ running
Signal parameters
- Expected behavior: continuous stream of pulses on the high‑resolution cam signal while cranking and running; pulses correlate to cam rotation
- Hall/logic style sensors: square wave ~0–5 V (or sensor supply dependent) with clean transitions
- Variable reluctance (VR) style sensors: AC waveform amplitude rises with RPM (may appear sine‑like); expected amplitude depends on sensor/design
- Pulse count/frequency: proportional to engine speed; the PCM expects a specific number of pulses per cam revolution — too few pulses (gaps or missing pulses) triggers the code
- Typical fault indicators on scope: missing pulses, long gaps, distorted/low amplitude signal, noisy or floating baseline
Diagnostic algorithm
- Confirm the code and capture freeze‑frame data. Clear codes and attempt to reproduce under the same conditions.
- Inspect sensor area: remove debris/oil and check reluctor/tone wheel for damage or looseness.
- Visually inspect wiring harness and connector; repair/clean as needed. Check for rodent damage, pin corrosion or pushed‑out terminals.
- Measure sensor supply voltage and ground at the connector with key ON; compare to specification (typically 5 V or switched supply for hall sensors).
- Backprobe the signal lead while cranking and capture with an oscilloscope. Verify pulse pattern, amplitude and count. Identify whether pulses are missing or intermittent.
- If pulses are missing, wiggle the harness and connectors while monitoring the signal to reproduce the fault; this helps find intermittent wiring faults.
- If waveform is weak or absent, test sensor resistance (for VR) and compare to spec, or substitute a known‑good sensor if available.
- Verify mechanical timing: confirm cam/crank timing marks and check for a jumped timing belt/chain or worn tensioners that would change pulse pattern.
- If wiring and sensor check good and timing is correct, inspect PCM grounds and power distribution. Consider PCM input circuit fault if all else checks good.
- After repairs, clear codes and road test under same conditions to confirm the fault does not return. Re‑scan for related codes and perform final scope comparison.
Likely causes
- High‑resolution cam position sensor failed or intermittent
- Reluctor/tone wheel physical damage, missing teeth or loose mounting
- Connector corrosion, pinbacking or chafed wiring causing intermittent signal loss
- Timing chain/belt jumped/failed causing loss of expected pulse pattern
Fault status
Status
PCM detected fewer than the expected high‑resolution timing pulses on Timing Reference A input; timing reference signal is incomplete or intermittent.
Repair difficulty: Medium
Diagnostic time: 0.5-3 hours
Similar codes
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Code
P0372
HUMMER
P — Powertrain
IC 24X Reference Circuit Missing Pulses
AI status
Completed
Completed
100%
Causes
- Faulty camshaft position (high-resolution) sensor
- Damaged or missing teeth on reluctor/tone wheel (cam or timing component)
- Wiring open/corroded/shorted or poor connector connection to the sensor
- Oil, debris or metal shavings fouling the sensor or reluctor wheel
- Timing chain/belt jumped or incorrect cam/crank mechanical timing
- Intermittent supply/ground or reference signal to the sensor
Symptoms
- Check Engine Light (MIL) illuminated and code P0372 stored
- Hard or no start, intermittent stalling or fails to start
- Rough idle, misfires or poor running under load
- Reduced engine performance or limp‑in mode
- Inaccurate ignition timing or advance behavior
- Possible multiple cam/crank correlation codes present
What to check
- Read freeze frame data and stored history for conditions when code set (RPM, load, temperature)
- Scan for other related codes (cam/crank correlation, cam/crank sensor faults)
- Visually inspect cam sensor, connector and wiring for damage, oil or corrosion
- Inspect reluctor/tone wheel for missing/damaged teeth, debris or loose mounting
- Check mechanical cam/crank timing (timing belt/chain condition and alignment marks)
- Backprobe sensor connector and verify reference voltage, ground and signal while cranking/ running
Signal parameters
- Expected behavior: continuous stream of pulses on the high‑resolution cam signal while cranking and running; pulses correlate to cam rotation
- Hall/logic style sensors: square wave ~0–5 V (or sensor supply dependent) with clean transitions
- Variable reluctance (VR) style sensors: AC waveform amplitude rises with RPM (may appear sine‑like); expected amplitude depends on sensor/design
- Pulse count/frequency: proportional to engine speed; the PCM expects a specific number of pulses per cam revolution — too few pulses (gaps or missing pulses) triggers the code
- Typical fault indicators on scope: missing pulses, long gaps, distorted/low amplitude signal, noisy or floating baseline
Diagnostic algorithm
- Confirm the code and capture freeze‑frame data. Clear codes and attempt to reproduce under the same conditions.
- Inspect sensor area: remove debris/oil and check reluctor/tone wheel for damage or looseness.
- Visually inspect wiring harness and connector; repair/clean as needed. Check for rodent damage, pin corrosion or pushed‑out terminals.
- Measure sensor supply voltage and ground at the connector with key ON; compare to specification (typically 5 V or switched supply for hall sensors).
- Backprobe the signal lead while cranking and capture with an oscilloscope. Verify pulse pattern, amplitude and count. Identify whether pulses are missing or intermittent.
- If pulses are missing, wiggle the harness and connectors while monitoring the signal to reproduce the fault; this helps find intermittent wiring faults.
- If waveform is weak or absent, test sensor resistance (for VR) and compare to spec, or substitute a known‑good sensor if available.
- Verify mechanical timing: confirm cam/crank timing marks and check for a jumped timing belt/chain or worn tensioners that would change pulse pattern.
- If wiring and sensor check good and timing is correct, inspect PCM grounds and power distribution. Consider PCM input circuit fault if all else checks good.
- After repairs, clear codes and road test under same conditions to confirm the fault does not return. Re‑scan for related codes and perform final scope comparison.
Likely causes
- High‑resolution cam position sensor failed or intermittent
- Reluctor/tone wheel physical damage, missing teeth or loose mounting
- Connector corrosion, pinbacking or chafed wiring causing intermittent signal loss
- Timing chain/belt jumped/failed causing loss of expected pulse pattern
Fault status
Status
PCM detected fewer than the expected high‑resolution timing pulses on Timing Reference A input; timing reference signal is incomplete or intermittent.
Repair difficulty: Medium
Diagnostic time: 0.5-3 hours
Similar codes
Repair manuals
Manual library for HUMMER
138
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