P0338

DTC P0338 CKP Sensor Circuit High Frequency




Circuit Description
The Crankshaft Position (CKP) Sensor is mounted in the front of the engine behind the harmonic balancer. The CKP sensor works in conjunction with a 3X (4x on V8 applications) reluctor wheel mounted on the front of the crankshaft. The CKP sensor has a B+ power supply, a ground, and a signal circuit.

As the crankshaft rotates, the reluctor wheel teeth interrupt a magnetic field produced by a magnet located in the sensor. The sensor's internal circuitry detects this field and produces a square wave which the VCM monitors on the signal circuit. The VCM uses this signal to accurately measure crankshaft velocity which is important to ignition control spark timing, fuel injector timing and for misfire detection.

If the CKP frequency is greater than expected by the VCM, this DTC will be set.

Conditions for Running the DTC
- The engine speed is less than 4,000 RPM.
- The MAF is 5 g/s or greater.

Conditions for Setting the DTC
The CKP sensor duty cycle is greater than a calibrated value.

Action Taken When the DTC Sets
The VCM illuminates the MIL after 2 consecutive driving cycles with the fault active

Conditions for Clearing the MIL/DTC
- A history DTC will clear if no fault conditions have been detected for 40 warm-up cycles (coolant temperature has risen 22 °C (40 °F) from the startup coolant temperature and the engine coolant temperature exceeds 70 °C (160 °F) during the same ignition cycle.
- Use the scan tool Clear Information function.

Diagnostic Aids
Inspect the face of the CKP sensor for metallic particles. This could result in an intermittent DTC.

Check for the following:
- A chipped or damaged reluctor wheel
- An incorrect reluctor wheel
- The incorrect alignment of the CKP sensor to reluctor wheel
- Excessive crankshaft end play Refer to Symptoms.

An intermittent may be caused by any of the following conditions:
- A poor connection
- Rubbed through wire insulation
- A broken wire inside the insulation

Thoroughly check any circuitry that is suspected of causing the intermittent complaint. Refer to Intermittents and Poor Connections Diagnosis.

If a repair is necessary, then refer to Wiring Repairs or Connector Repairs.

Steps 1 - 4:

Steps 5 - 8:

Steps 9 - 10:

Test Description
The number(s) below refer(s) to the step number(s) on the diagnostic table.
2. It is very difficult to start an engine with a crank sensor high duty cycle failure. A running engine, however, may not be adversely affected by a high duty cycle failure.
3. This step determines if DTC P0338 is the result of a hard failure or an intermittent condition.
4. This test checks the crank sensor for too high of a duty cycle.