DTC P1374 Crankshaft Position (CKP) High to Low Resolution Frequency Correlation l
Circuit Description
The ignition control module (ICM) generates the 3X reference signal from the 18X crankshaft position 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 PCM. The PCM uses this signal to initiate fuel injector pulses and calculate engine speed and crankshaft position at engine speeds above 1200 RPM (± 150 RPM). The PCM compares the number of 3X reference pulses to the number of 18 X reference and CAM signal pulses being received. If the PCM receives an incorrect number of pulses on the 3X reference circuit, DTC P1374 will set and the PCM will use the 18X reference signal circuit for fuel and ignition control. The engine will continue to start and run using the 18X reference and Camshaft Position PCM input signals only.
Conditions for Running the DTC
The engine has been 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 will illuminate the MIL during the second consecutive trip in which the DTC test has run and failed. |
| • | The PCM will use the 18X reference signal circuit for fuel and ignition control. |
| • | If equipped with traction control, the PCM will command the EBTCM via Class 2 serial data to turn OFF traction control, and the EBTCM will illuminate the TRACTION OFF lamp. |
| • | 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 the scan tool Clear Info function or by disconnecting the PCM battery feed. |
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:
| • | Poor connection. |
| Inspect the PCM 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 3X 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. |
| • | 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 . |
| • | Secondary ignition wire(s) arcing to wiring harness. |
| Check 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.
Step | Action | Value(s) | Yes | No | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
1 | Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | ||||||||||
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? | -- | Refer to Diagnostic Aids | |||||||||
4 |
Does the injector test light 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 . Is action complete? | -- | -- | |||||||||
Replace the PCM. Important:: The replacement PCM must be programmed. Refer to Powertrain Control Module Replacement/Programming . Is action complete? | -- | -- | ||||||||||
11 |
Does the scan tool indicate DTC P1374 failed? | -- | System OK |
