Refer to
Ignition Control Module, CMP and CKP
Circuit Description
The ignition control module (ICM) generates the 3X reference signal from the 18X crankshaft position (CKP) sensor. To generate the 3X reference signal, the ICM processes the 18X CKP signal through a divide-by-6 circuit. The ICM then sends the 3X reference signal to the powertrain control module (PCM). The PCM uses this signal to initiate fuel injector pulses and calculate the engine speed and CKP at engine speeds above 1200 RPM (± 150 RPM). The PCM compares the number of 3X reference pulses to the number of 18X reference and CAM signal pulses being received. If the PCM receives an incorrect number of pulses on the 3X reference circuit, DTC P1374 is set and the PCM uses the 18X reference signal circuit for fuel and ignition control. The engine continue to start and run using the 18X reference and camshaft position (CMP) signals only.
Conditions for Running the DTC
The engine is running for longer than 3 seconds.
Conditions for Setting the DTC
| • | The ratio of 18X reference pulses to CAM signal pulses received by the PCM equals 36:1. |
| • | The ratio of 18X reference pulses to 3X reference pulses received by the PCM does not equal 6:1. |
| • | The above conditions are present for up to 30 seconds. |
Action Taken When the DTC Sets
| • | The PCM illuminates the malfunction indicator lamp (MIL) during the second consecutive trip in which the DTC test has run and failed. |
| • | The PCM uses the 18X reference signal circuit for fuel and ignition control. |
| • | If the vehicle is equipped with traction control, the PCM commands the EBCM, via Class 2 serial data, to turn 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. |
Conditions for Clearing the MIL/DTC
| • | The PCM turns the MIL off during the third consecutive trip in which the diagnostic has run and passed. |
| • | The history DTC clears after 40 consecutive warm-up cycles have occurred without a malfunction. |
| • | The DTC may be cleared by using the scan tool Clear Info function or by disconnecting the PCM battery feed. |
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:
| • | Inspect the PCM harness and connectors for improper mating, broken locks, improperly formed or damaged terminals, and faulty terminal to wire connections. |
| • | 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 3X 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. |
| • | Inspect for a 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. Refer to Ignition Coil Replacement . |
| • | Inspect for secondary ignition wires arcing to the 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
The number(s) below refer to the step number(s) on the Diagnostic Table.
Step | Action | Value(s) | Yes | No | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | ||||||||||
2 |
Important: If any other DTCs are set, diagnose the other DTCs first. Attempt to start the engine. Does the engine start and continue to run? | -- | ||||||||||
3 |
Does the scan tool indicate DTC P1374 Failed This Ign? | -- | Go to Diagnostic Aids | |||||||||
4 |
Does the injector test lamp blink? | -- | ||||||||||
5 |
Was a problem found? | -- | ||||||||||
6 |
Was a problem found? | -- | ||||||||||
7 |
Was a problem found? | -- | ||||||||||
8 |
Was a problem found? | -- | ||||||||||
9 | Replace the ignition control module. Refer to Ignition Control Module Replacement . Did you complete the repair? | -- | -- | |||||||||
|
Important:: The replacement PCM must be programmed. Refer to Powertrain Control Module Replacement/Programming . Replace the PCM. Did you complete the repair? | -- | -- | ||||||||||
11 |
Does the scan tool indicate DTC P1374 failed? | -- | System OK |
