P0372
Timing Reference High Resolution Signal A Too Few Pulses
The appearance of the standard OBD2 trouble fault code P0372 is an indicator that your vehicle ECU triggered a threshold alert for "Timing Reference High Resolution Signal A Too Few Pulses". Understanding the root component breakdown helps avoid expensive diagnostic fees.
Driver's Summary
Your vehicle's computer logged P0372 after detecting a malfunction in the timing reference high resolution signal a too few pulses system. In practice, this fault causes engine misses, dies, or won't start. This is not a code to ignore — the underlying fault can rapidly worsen and lead to costly repairs if driving continues.
Symptoms
Engine misses, dies, or won't start
Common Causes
- Broken teeth on optical disc or reluctor wheel
- Failing high resolution sensor
- Open circuit in signal wire
- Loose sensor mounting
How to Fix
- 1 Inspect and replace optical disc
- 2 Replace high resolution sensor
- 3 Repair broken signal wire
- 4 Tighten sensor hardware
Technical Explanation
The ECM detects code P0372 by continuously monitoring the relevant sensor circuit against calibrated threshold values stored in its non-volatile memory. The PCM monitors crankshaft rotational velocity via the CKP sensor at a resolution of individual tooth gaps on the reluctor ring. A combustion event in each cylinder produces a measurable acceleration spike; its absence or weakness is flagged as a misfire event within a 200-revolution or 1000-revolution test window. The fault remains stored in memory even after the MIL is cleared; it becomes a confirmed DTC after failing two consecutive drive cycles, and the PCM logs a freeze frame record of the engine's exact operating state at the moment of detection.
Is It Safe to Drive?
This fault carries real mechanical risk. The root causes — including broken teeth on optical disc or reluctor wheel — can trigger a chain reaction of component failures if the vehicle continues to be driven. Have it towed or drive directly to a shop without delay.
Mechanic's Pro Tip
The most common mistake with P0372 is replacing the sensor without verifying the reference voltage and ground integrity first. Use a scan tool to monitor the sensor's live output; a truly failed sensor shows a stuck, flatlined reading — a sensor that fluctuates but reads slightly off usually indicates a wiring or vacuum issue, not a dead sensor. Always spray electrical contact cleaner on the connector pins before condemning the sensor.
Sensor replacement: 150 - 400