P0373 Timing Reference High Resolution Signal A Intermittent/Erratic Pulses

P0373 points to intermittent or erratic pulses in Timing Reference High Resolution Signal A. The timing reference is unstable enough to affect engine position tracking.

Code details

Generic OBD-II · P0

System: Ignition / Misfire
Code type: Generic (SAE / ISO controlled)
Standard: SAE J2012 / ISO 15031-6

Diagnostic boundary

A diagnostic trouble code reports that a monitored test failed. It does not prove one specific part is bad, and manufacturer logic can add vehicle-specific conditions.

Do not clear P0373 after a brief idle check if the failure only appears while driving or after heat soak.

Symptoms of P0373

Rough idle, shaking, or a stumble under acceleration.
A flashing check-engine light during an active misfire.
Power loss and higher fuel consumption.

Common causes of P0373

Worn spark plugs, ignition coils, or plug wires.
Fuel-delivery problems — injectors, pressure, or a lean/rich mixture.
Vacuum leaks, low compression, or a mechanical fault in that cylinder.

Useful checks before replacing parts

Review stall, surge, misfire-like symptoms, RPM instability, freeze-frame data, and whether signal A errors happen with heat, vibration, or moisture.
Inspect wiring flex points, shielding, connector tension, sensor mounting, trigger wheel damage, grounds, and harness routing near high-current components.
Record the waveform during road-load and heat-soak testing to catch erratic pulse spacing or momentary dropout.

Related OBD-II codes

These nearby ignition / misfire entries can help compare wording and pin down the fault area.