P0370 Timing Reference High Resolution Signal A Malfunction

P0370 indicates a malfunction in Timing Reference High Resolution Signal A. The controller is not seeing the expected high-resolution timing reference used for precise engine speed and 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 replace fuel or ignition parts for a stall or no-start until the timing reference signal path has been tested.

Symptoms of P0370

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 P0370

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

Compare high-resolution signal A data, crankshaft position signal, cam sync, RPM stability, freeze-frame RPM, and any no-start or stall symptoms.
Inspect sensor power, ground, signal wiring, shielding, tone wheel or optical disc condition, connector fit, and module input pins.
Use a scope to verify waveform shape, pulse spacing, amplitude, and dropouts during cranking and running.

Related OBD-II codes

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