P0336

Circuit Description
The 18X reference signal is produced by the ignition control module (ICM). The ICM calculates the 18X reference signal by filtering the crankshaft position (CKP) sensor 18X pulses when the engine is running and the CKP sync pulses are being received. The powertrain control module (PCM) uses the 18X reference signal to calculate the engine RPM and the CKP 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 is set and the PCM uses the 3X reference signal circuit for fuel and ignition control. The engine continues to start and run using the 3X reference and CAM signals only.

Conditions for Running the DTC
The engine is running and 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 are present for 290 occurrences.

Action Taken When the DTC Sets
^ The PCM illuminates the malfunction indicator lamp (MIL) during the second consecutive trip in which the diagnostic test has run and failed.
^ The PCM stores the conditions which were present when the DTC set as Freeze Frame and Fail Records data.

Action Taken When the DTC Sets
^ The PCM illuminates the MIL during the second consecutive trip in which the diagnostic test has run and failed.
^ The PCM uses the 3X reference signal circuit for fuel and ignition control.
^ If equipped with traction control, the PCM commands the EBCM, via Class 2 serial data, to set an ABS/TCS DTC. The EBCM turns off the traction control and illuminates the TRACTION OFF lamp.
^ The PCM stores the conditions which were present when the DTC set as Freeze Frame and Fail Records data.

Diagnostic Aids
An intermittent may be caused by a faulty connection, rubbed through wire insulation, or a wire broken inside the insulation. Inspect for the following conditions:
^ A faulty connection. Inspect the PCM harness and connectors for improper mating, broken locks, improperly formed or damaged terminals, and faulty terminal to wire connection.
^ A 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 the connectors and wiring harnesses related to the ICM. A change in voltage indicates the location of the malfunction.
^ A misrouted wiring harness. Inspect the ICM harness to ensure that it is not routed near secondary ignition components.
^ A malfunctioning ignition coil. Remove the ignition coils and inspect the ICM and the coils for cracks, carbon tracking, or Other signs that indicate that the coil secondary circuit is arcing to the ICM or the ICM wiring harness.
^ Any secondary ignition wires arcing to wiring harness. Inspect the secondary ignition wires for carbon tracking or Other signs of damage.
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.