P0373
Timing Reference High Resolution Signal A Intermittent/Erratic Pulses
Encountering the engine check light code P0373 signifies an explicit mechanical or electrical operational breakdown categorized as "Timing Reference High Resolution Signal A Intermittent/Erratic Pulses". Professional scanner tools usually flag this subsystem loop early on.
Driver's Summary
A P0373 fault code points directly to a problem with timing reference high resolution signal a intermittent/erratic pulses that the ECM has confirmed over multiple drive cycles. You may notice intermittent stalling, hesitation, check engine light, all of which are direct consequences of this malfunction. This condition is classified as high severity. Prompt diagnosis is essential to prevent cascading damage to related components.
Symptoms
Intermittent stalling, hesitation, check engine light
Common Causes
- Loose wiring connection
- Moisture in the sensor housing
- Failing sensor
- Excessive end play in distributor shaft
How to Fix
- 1 Secure electrical connections
- 2 Dry sensor housing and seal
- 3 Replace optical sensor
- 4 Rebuild or replace distributor
Technical Explanation
To set P0373, the PCM samples the affected circuit multiple times per second, comparing live readings against manufacturer-programmed operating windows. Misfire rate is counted per cylinder over rolling windows and compared against two thresholds: a catalyst-damaging rate (triggers flashing MIL) and an emissions-exceeding rate (triggers solid MIL). The PCM logs which cylinder is misfiring based on crankshaft position at the time of each detected event. After two failed drive cycles, the code transitions from a pending to a confirmed DTC, and the PCM activates the MIL. Clearing the code without repairing the fault will result in re-illumination within one to two complete drive cycles.
Is It Safe to Drive?
With P0373 active, your engine or transmission is not operating within design parameters. Short-term driving may seem fine, but internal damage is accumulating — particularly to loose wiring connection.
Mechanic's Pro Tip
The most common mistake with P0373 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.
Wiring repair: 100; Distributor rebuild: 200 - 400