Faulty camshaft or crankshaft position sensor; Damaged or corroded wiring or connectors in the sensor circuit; Worn or damaged reluctor wheel (tone ring) on the camshaft or crankshaft; Electrical interference or poor ground connection; Failed ECM (rare but possible); Debris or metal particles on the sensor tip; Loose or improperly installed sensor

DTC codes / P03xx · Ignition system and misfire / P0373

P0373Timing Reference High Resolution Signal 'A' Intermittent/Erratic Pulses

P0373 indicates that the engine control module (ECM) has detected intermittent or erratic pulses from the high-resolution timing reference signal 'A', which is typically generated by the camshaft or crankshaft position sensor. The ECM uses this signal to precisely determine engine position for fuel injection and ignition timing, so an unstable signal can disrupt these critical functions.

SystemPowertrain

Code typeGeneric (all makes)

SeverityMedium

Fix difficultyIntermediate

AreaIgnition system and misfire

Symptoms you may notice

Illumination of the check engine light, often with no other noticeable symptoms
Engine may stall or misfire intermittently, especially at idle or low speeds
Rough running or hesitation during acceleration
Difficulty starting or extended cranking time
Poor fuel economy or increased emissions
In some cases, the engine may enter limp mode or have reduced power

Common causes, most likely first

Faulty camshaft or crankshaft position sensor
Damaged or corroded wiring or connectors in the sensor circuit
Worn or damaged reluctor wheel (tone ring) on the camshaft or crankshaft
Electrical interference or poor ground connection
Failed ECM (rare but possible)
Debris or metal particles on the sensor tip
Loose or improperly installed sensor

How to diagnose and fix it

Perform a visual inspection of the sensor and its wiring for obvious damage, corrosion, or loose connections
Use an OBD-II scanner to check for related codes and freeze-frame data to identify the conditions when the fault occurred
Test the sensor's resistance and signal output with a multimeter or oscilloscope according to the manufacturer's specifications
Inspect the reluctor wheel for missing teeth, cracks, or debris buildup
Check the sensor's air gap and mounting condition
Repair or replace damaged wiring or connectors as needed
Replace the faulty sensor if testing confirms it is not producing a consistent signal

Overlooked Causes of Erratic Timing Signals

A common oversight is assuming the sensor is at fault when the real problem is a damaged reluctor wheel or excessive air gap, which can mimic sensor failure.
Electrical interference from aftermarket accessories or poor grounding can cause erratic signals that set P0373 without any physical sensor fault.
The code can be set by a loose or improperly installed sensor that intermittently loses signal due to vibration, so always check mounting torque.
On some vehicles, a failing camshaft phaser or timing chain tensioner can cause erratic cam sensor signals, leading to P0373 even though the sensor itself is good.
P0373 is often accompanied by other timing-related codes, so diagnosing it in isolation may lead to misrepair; always check for stored and pending codes.

Can I keep driving with P0373?

If the check engine light is on but the engine runs normally, you can drive cautiously to a repair shop, but avoid heavy acceleration or long trips. If the engine stalls, misfires, or loses power, stop driving and have the vehicle towed to prevent safety risks and further damage.

Tools that help

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Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.