P0372 OBD-II Trouble Code: Timing Reference High Resolution Signal A Too Few Pulses

P0372 code definition

P0372 is the OBD-II trouble code for Timing Reference High Resolution Signal A too few pulses.

What the P0372 code means

The Powertrain Control Module (PCM) provides control and timing for the fuel injection system in part by monitoring signals sent by the optical sensor. This sensor sends a high resolution signal to the PCM indicating how many pulses have been detected on the sensor disk on the injection pump.

There should be about 64 pulses for every cam pulse, and when the number actually detected deviates from this norm, the P0372 or another P0370 series code will store. The letter A simply indicates an area of the involved circuitry rather than a specific component.

What causes the P0372 code?

Conditions that may cause this Diagnostic Trouble Code (DTC) include:

• A faulty camshaft or camshaft sensor

• A faulty crankshaft or crankshaft sensor

• Bad distributor position sensors

• An open or short in the timing reference optical sensor harness

• A faulty optical sensor

• Loose or damaged connections in the timing reference optical sensor circuitry

• Mechanical failure in the distributor (most common in rear-wheel drive, high mileage vehicles)

• PCM failure (rare)

Sensor failure is typically the most common cause of this trouble code. Still, a thorough diagnostic investigation should be carried out, as car problems often have more than one cause.

What are the symptoms of the P0372 code?

There may be no detectable symptoms at all, or there may be engine misfires, spark knock during acceleration, or decreased fuel efficiency. While the code will likely store upon the first occurrence, it may take some time before the Check Engine light comes on, so it’s important to be aware of any noticeable signs of a problem.

How does a mechanic diagnose the P0372 code?

Diagnostic procedure for this code may include:

• Verifying that the DTC is stored, and recording the freeze frame data using a scan tool

• Clearing any stored codes and then road testing the vehicle to see if they return

• Visually observing the tachometer with the engine running to see if there is an RPM signal

• Visually inspecting the crankshaft position sensor, crankshaft gear, and connectors and wiring for damage

• Testing the Crankshaft Position Sensor (CPS) system to ensure the reference voltage matches specifications

• Using an ohmmeter to check for system continuity

• If necessary, inspecting the distributor for damage, wobble, or too much end-play

Common mistakes when diagnosing the P0372 code

Sometimes the crankshaft, camshaft, and distributor sensors will be replaced unnecessarily when the problem actually lies in a distributor malfunction. Neglecting to test the crank and cam reluctor rings when replacing sensors is also a common oversight.

How serious is the P0372 code?

Any malfunction which interferes with proper fuel injection timing and engine function should be considered serious. Because of the specialized diagnostic and repair tools often required for this type of problem, it’s best to have a qualified technician look at the vehicle as soon as possible.

What repairs can fix the P0372 code?

Possible solutions for this DTC include:

• Camshaft, distributor hall effect, and crankshaft sensor replacement
• Replacement of corroded or damaged wiring or connectors
• Distributor replacement

Additional comments for consideration regarding the P0372 code

If you decide to tackle the diagnostic process yourself, be sure that you disconnect the wiring connectors from the PCM side before checking resistance values on the harness side. This will prevent damage to the PCM.

When replacing crankshaft or camshaft sensors, be sure to replace them as a set, rather than individually.

The cause of DTC P0372 can be complicated and time-consuming to track down and repair. The task may involve multiple repairs, as well as specialized tools and equipment. If you suspect this repair is beyond your skill level, it’s best to contact a qualified mechanic and have them assess the issue instead.

Need help with a P0372 code?

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