P0371 - Timing Reference High Resolution Signal A Too Many Pulses
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System
Powertrain (Engine & Gearbox)
Related Fault Codes
Technical Description
P0371 is set when the Engine Control Module (ECM/PCM) detects more pulses than expected from the high-resolution timing reference signal A. This signal is typically generated by an optical sensor or a high-frequency crankshaft/camshaft sensor. The ECM uses this signal for precise fuel injection and ignition timing. If the pulse count exceeds the calibrated threshold per engine revolution, the ECM loses synchronization integrity, which often triggers a limp-home mode to prevent engine damage caused by incorrect timing.
Possible Causes
Electromagnetic interference (EMI) on the signal wire from ignition components or alternator
Faulty high-resolution sensor (optical or magnetic sensor internal failure)
Damaged or dirty reluctor wheel/encoder disk causing false pulses
Poor connection or corrosion in the sensor wiring harness connector
Symptoms
Recommended Solution
Workflow
Mechanic's Tip
Before replacing expensive components, always double-check wiring and connections. 80% of all sensor faults are actually due to corroded contacts or broken wires.
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