P0336

Circuit Description
The 18X reference signal is produced by the ignition control module. The ICM calculates the 18X reference signal by filtering the Crankshaft Position (CKP) sensor 18X pulses when the engine is running and CKP sync pulses are also being received. The PCM uses the 18X reference signal to calculate engine RPM and crankshaft position at engine speeds below 1200 RPM. The PCM constantly monitors the number of pulses on the 18X reference circuit and compares the number of 18X reference pulses to the number of 3X reference pulses and CAM signal pulses being received. If the PCM receives an incorrect number of pulses on the 18X reference circuit, DTC P0336 will set and the PCM will use the 3X reference signal circuit for fuel and ignition control. The engine will continue to start and run using the 3X reference and CAM signals only.

Conditions for Running the DTC
The engine is running (3X reference pulses are being received).

Conditions for Setting the DTC
^ The ratio of 18X reference pulses to 3X reference pulses received by the PCM does not equal 6 to 1.
^ The ratio of 3X reference pulses to CAM signal pulses received by the PCM equals 6 to 1.
^ Above conditions for 290 of 300 test samples.

Action Taken When the DTC Sets
^ The PCM will illuminate the MIL during the second consecutive trip in which the diagnostic test has been run and failed.
^ The PCM will store conditions which were present when the DTC set as Freeze Frame and Fail Records data.

Conditions for Clearing the MIL/DTC
^ The PCM will turn the MIL OFF during the third consecutive trip in which the diagnostic has been run and passed.
^ The history DTC will clear after 40 consecutive warm-up cycles have occurred without a malfunction.
^ The DTC can be cleared by using a scan tool.

Conditions for Clearing the MIL/DTC
^ The PCM will turn the MIL OFF during the third consecutive trip in which the diagnostic has been run and passed.
^ The history DTC will clear after 40 consecutive warm-up cycles have occurred without a malfunction.
^ The DTC can be cleared by using a scan tool.

Diagnostic Aids
An intermittent may be caused by a poor connection, rubbed through wire insulation or a wire broken inside the insulation. Check for the following conditions:
^ Rotate the engine crankshaft until the 18X sensor has voltage greater than 4 volts before performing Diagnostic Aids.
^ Poor connection at the PCM, ignition control module, or CKP sensor.
Inspect the harness and connectors for improper mating, broken locks, improperly formed or damaged terminals, and poor terminal to wire connection.
^ Damaged harness.
Inspect the wiring harness for damage. If the harness appears to be OK, disconnect the PCM, turn the ignition on and observe a voltmeter connected to the 18X reference circuit at the PCM harness connector while moving connectors and wiring harnesses related to the ICM. A change in voltage will indicate the location of the malfunction.
^ Incorrect harness routing near secondary ignition components.
^ Secondary ignition wire(s) arcing to wiring harness.
Check secondary ignition wires for carbon tracking or other signs of damage.
^ Malfunctioning Ignition Coil.
Remove the ignition coils and inspect the ignition control module and coils for cracks, carbon tracking, or other signs that indicate that the coil secondary circuit is arcing to the ICM or ICM wiring harness.
Reviewing the Fail Records vehicle mileage since the diagnostic test last failed may help determine how often the condition that caused the DTC to be set occurs. This may assist in diagnosing the condition.

Test Description
Number(s) below refer to the step number(s) on the Diagnostic Table.
10. This vehicle is equipped with a PCM which utilizes an Electrically Erasable Programmable Read Only Memory (EEPROM). When the PCM is being replaced, the new PCM must be programmed. Refer to PCM Replacement/Programming.