P0373 means the powertrain control module sees an unstable, dropping, or erratic signal from the engine’s high-resolution timing reference sensor. That sensor provides the fine crankshaft-position or engine-speed information the PCM needs for ignition timing, fuel injection timing, and misfire detection. An intermittent signal can cause driveability problems even though the sensor has not completely failed.
The crankshaft/camshaft position sensor or optical timing encoder can produce weak, noisy, or dropout-prone output as its coil, optical element, or internal wiring degrades. This is the most common root cause of an intermittent timing-reference signal.
Intermittent opens, poor pin fit, corrosion, chafed insulation, or damaged shielding in the sensor harness can make the signal drop out only under vibration, heat, or moisture. Connector inspection and pin-tension checks often reveal the problem.
A cracked, chipped, corroded, or debris-covered reluctor wheel, an incorrect sensor air gap, or a loose sensor mount can produce missing or erratic pulses as the wheel rotates.
A weak sensor supply voltage, poor engine or PCM ground, or electromagnetic interference from nearby ignition or charging components can corrupt the high-resolution signal and make it appear intermittent.
If the sensor, wiring, and mechanical inputs all test normal and the PCM still interprets a good signal as erratic, an internal PCM input-circuit problem is possible, but this is uncommon and should be confirmed before replacement.
Usually not. The sensor, its wiring, or the reluctor wheel is the far more likely cause. PCM replacement is commonly recommended but often turns out to be a misdiagnosis unless everything else has been verified good.
It is not advisable. An intermittent timing signal can cause stalling, hard starting, or a no-start condition. Have it diagnosed before relying on the vehicle.
Not always. The exact high-resolution timing sensor varies by engine, and wiring, connector, or reluctor-wheel problems are equally or more common than a failed sensor itself.
The PCM still receives some pulses, but they are irregular, noisy, or briefly drop out. That points to a failing sensor, loose connection, or mechanical trigger issue rather than a completely dead circuit.