The powertrain control module (PCM) uses dual crankshaft position (CKP) A and CKP B sensors to determine crankshaft position. The PCM supplies an ignition voltage and a ground for each sensor. During engine rotation, a slotted ring, machined into the crankshaft, causes the sensors to return a series of ON and OFF pulses to the PCM. The PCM uses these pulses to decode the position of the engine crankshaft.

The PCM uses 2 basic methods of decoding the engine position, Angle Based and Time Based, using either CKP A or CKP B sensor input. During normal operation, the PCM uses the angle based method. In order to operate in this mode, the PCM must receive signal pulses from both CKP sensors. The PCM uses the signal pulses to determine an initial crankshaft position, and to generate medium resolution (24X reference) and low resolution (4X reference) signals. Once the initial crank position is determined, the PCM continuously monitors both sensors for valid signal inputs. As long as both signal inputs remain, the PCM will continue to use the Angle Based mode.

When either CKP signal is lost, the PCM will compare the medium resolution signal to the camshaft position (CMP) sensor signal. If the PCM detects a valid CMP signal, and the medium resolution to CMP signal correlation is correct, the PCM determines that CKP sensor A is at fault. However, if the medium resolution to CMP correlation is incorrect, the PCM determines that CKP sensor B is at fault. If the PCM determines that CKP sensor B is at fault, DTC P0385 will set. The PCM will switch from Angle Based mode to Time Based mode A using CKP sensor A signal input. If, after switching to Time Base A mode, the PCM detects an intermittent loss of CKP sensor A signal, DTC P0336 will set.

This diagnostic procedure supports the following DTC:

DTC P0336 Crankshaft Position (CKP) Sensor A Performance

The PCM detects 5 CKP resyncs have occurred within 10 seconds.

The following conditions may cause this DTC to set:

Excess crankshaft end play will cause the CKP sensor reluctor wheel to move out of alignment with the CKP sensor. This could result in any of the following conditions:

An improperly installed crankshaft could cause excess crankshaft end play.

If the condition is intermittent, refer to Intermittent Conditions .

Procedures for Selecting Crank Position Sensing Decode Mode

When diagnosing the CKP sensors, enabling a specific decode mode (Angle, Time A, or Time B) may be necessary. To enable a specific crank decode using the scan tool, perform the following steps:

1. Turn ON the ignition, with the engine OFF.
2. Select Engine Output Controls.
3. Select Crank Position Sensing Decode Mode.
4. Select the desired mode (Angle, Time A, or Time B), and press Select State.
5. Command the decode mode by pressing Command State.

The commanded state remains valid for the current ignition cycle. A specific decode mode cannot be commanded with the engine running, or after commanding a desired decode mode. To command a different decode mode, you must cycle the ignition OFF and ON.

The numbers below refer to the step numbers on the diagnostic table.

2. During normal operation, the PCM uses the Angle Mode to determine engine position. In order to operate in this mode, the PCM must receive valid input from both CKP sensors. If the PCM detects a loss of CKP sensor  A signal, the PCM switches to a Time B mode using CKP sensor B input to determine engine position. If the PCM detects a loss of CKP sensor B, the PCM switches to a Time A mode using CKP sensor A input to determine engine position. If the PCM detects a loss of CKP sensor B signal, DTC P0385 will set. DTC P0336 will only set if a problem with CKP sensor A occurs while in Time A mode. DTC P0385 must be diagnosed first.

6. To properly verify any repair to CKP sensor A harness connectors, the system must be commanded to operate in Time A mode. This forces the PCM to use CKP sensor A to determine engine position. If the system is functioning normally, DTC P0336 should not reset.