Quick answer: The P0371 code indicates that the engine control module has detected too many high-resolution timing reference pulses from the ignition distributor or position sensor. It affects the engine’s ignition and fuel delivery system. This is a high-urgency issue that can cause severe misfires, stalling, or a no-start condition.
If your check engine light triggered the P0371 code, your engine’s computer is having trouble determining precise crankshaft or camshaft timing. This guide breaks down what the code means, the common warning signs, and how to accurately diagnose and resolve the problem without throwing money at unnecessary parts.
What Does P0371 Mean?
To control ignition timing and fuel injection with precision, the Powertrain Control Module (PCM) relies on timing reference signals. Typically, these signals are broken down into high-resolution (high-count) and low-resolution (low-count) pulses sent by an optical or magnetic sensor. The P0371 code triggers when the PCM receives significantly more high-resolution pulses than expected relative to the low-resolution signal. Electrical noise, optical rotor damage, or sensor failure can create extra false pulses, confusing the computer and disrupting normal engine operation.
Symptoms
- Check Engine Light illuminated on the dashboard
- Engine stalling during idle or while driving
- Hard starting or complete refusal to start
- Engine hesitation, jerking, or severe misfiring during acceleration
- Rough or unstable engine idling
Possible Causes
The most common mistake with this code is replacing the main distributor assembly or sensor immediately without testing the wiring harness for electrical interference or loose connections.
- Damaged or corroded wiring harness, loose ground, or short circuits near the timing sensor.
- Faulty high-resolution timing reference sensor or optical distributor unit.
- Moisture, engine oil, or metal debris contaminating the optical sensor disc or pickup.
- Electromagnetic interference (EMI) caused by worn spark plug wires routed too close to sensor signal wires.
- Failed Powertrain Control Module (PCM) or outdated PCM software.
Check These Yourself Before Visiting a Mechanic
- Inspect the electrical connector leading to your ignition distributor or crank sensor for loose pins, corrosion, oil contamination, or cracked insulation.
- Verify that high-voltage spark plug wires are properly routed and not resting directly against the timing sensor signal wiring, which causes signal interference.
- Check battery terminals and main engine ground connections to ensure clean, tight contacts.
How to Fix It
- Scan the vehicle for additional related ignition codes and record freeze-frame data.
- Inspect the sensor wiring harness and ground connections for physical damage, corrosion, or pin tension issues.
- Use a digital multimeter or oscilloscope to monitor the high-resolution signal wire for false voltage spikes or electrical noise while wiggling the harness.
- Inspect the optical sensor or rotor inside the distributor assembly for oil penetration, rust, or physical debris.
- Replace the faulty timing reference sensor or complete distributor assembly if signal output remains erratic.
- Re-test the system and clear the trouble code using an OBD-II scanner.
Estimated Repair Costs (2026)
| Job | Parts ($) | Labor ($) |
|---|---|---|
| Wiring Repair / Cleaning Connectors | $10 – $30 | $100 – $200 |
| High-Resolution Timing Sensor Replacement | $80 – $220 | $120 – $250 |
| Ignition Distributor Assembly Replacement | $250 – $600 | $150 – $350 |
| PCM Diagnosis & Replacement | $400 – $900 | $150 – $300 |
Note: These are estimated 2026 repair costs in US dollars; actual prices vary depending on your vehicle make, model, and location.
Frequently Asked Questions
Can I drive with the P0371 code?
No, driving with this code is not recommended. Because the engine computer relies on this high-resolution signal to time spark and fuel, the vehicle can stall suddenly while driving or fail to restart, posing a safety risk.
How do I clear the P0371 code?
You can clear the code using an OBD-II scan tool after repairing the underlying cause. However, if the timing signal discrepancy persists, the PCM will illuminate the check engine light again within a few crank cycles.
What causes extra pulses in a timing signal?
Extra pulses are typically caused by electrical interference bleeding into the signal wire, a cracked or dirty optical disc inside the sensor, or loose wiring pins that create rapid intermittent connections.