DTC P1374 Crankshaft Position (CKP) High to Low Resolution Frequency Correlation

Refer to Engine Controls Schematics CKP, CMP, ICM, Bank 1 KS and Bank 2 KS

Circuit Description

The 3X reference signal is produced by the ignition control module. The ICM calculates the 3X reference signal by dividing the crankshaft position (CKP) sensor 18X pulses by 3 when the engine is running and when CKP sync pulses are also being received. The PCM uses the 3X reference signal in order to calculate engine RPM and the crankshaft position at engine speeds above 1200RPM. The PCM also uses the pulses on this circuit in order to initiate the injector pulses. The PCM constantly monitors the number of pulses on the 3X reference circuit, and compares the number of 3X reference pulses to the number of 18X reference pulses and CAM signal pulses being received. If the PCM receives an incorrect number of pulses on the 3X reference circuit, 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. DTC P1374 will set.

Conditions for Running the DTC

The engine has been running for more 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 conditions are present for more than 10 seconds.

Action Taken When the DTC Sets

The PCM will illuminate the malfunction indicator lamp (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/Failure Records data.

Conditions for Clearing the MIL/DTC

The PCM will turn OFF the malfunction indicator lamp (MIL) during the third consecutive trip in which the diagnostic has 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

Test for the following conditions:

•	A malfunctioning ignition coil--Remove the ignition coils and inspect the ignition control module and the coils for cracks, carbon tracking, or for other signs that indicate that the coil secondary circuit is arcing to the ICM or to the ICM wiring harness. Refer to Ignition Coil(s) Replacement .

•	The secondary ignition wires arcing to wiring harness--Inspect the secondary ignition wires for carbon tracking or for other signs of damage.

Many situations may lead to an intermittent condition. Perform each inspection or test as directed.

Important: : Remove any debris from the connector surfaces before servicing a component. Inspect the connector gaskets when diagnosing or replacing a component. Ensure that the gaskets are installed correctly. The gaskets prevent contaminate intrusion.

•	Loose terminal connection

-	Use a corresponding mating terminal to test for proper tension. Refer to Testing for Intermittent Conditions and Poor Connections , and to Connector Repairs in Wiring Systems for diagnosis and repair.

Inspect the harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and faulty terminal to wire connection. Refer to Testing for Intermittent Conditions and Poor Connections , and to Connector Repairs in Wiring Systems for diagnosis and repair.

•

Damaged harness--Inspect the wiring harness for damage. If the harness inspection does not reveal a problem, observe the display on the scan tool while moving connectors and wiring harnesses related to the sensor. A change in the scan tool display may indicate the location of the fault. Refer to Wiring Repairs in Wiring Systems for diagnosis and repair.

•	Inspect the powertrain control module (PCM) and the engine grounds for clean and secure connections. Refer to Wiring Repairs in Wiring Systems for diagnosis and repair.

If the condition is determined to be intermittent, reviewing the Snapshot or Freeze Frame/Failure Records may be useful in determining when the DTC or condition was identified.

Test Description

The numbers below refer to the step numbers on the Diagnostic Table.

10. This vehicle is equipped with a PCM which utilizes an electrically erasable programmable read-only memory (EEPROM). When you replace the PCM, you must program the new PCM.

DTC P1374 - 3X Reference Circuit

Step

Action

Values

Yes

Did you perform the Powertrain On-Board Diagnostic (OBD) System Check?

Go to Step 2

Go to Powertrain On Board Diagnostic (OBD) System Check

Attempt to start the engine.

Does the engine start and continue to run?

Go to Step 3

Go to Engine Cranks but Does Not Run

Review and record the scan tool Failure Records data.
Operate the vehicle within the Failure Records conditions.
Use the scan tool in order to monitor the Specific DTC information for DTC P1374.

Does the DTC reset?

Go to Step 4

Go to Diagnostic Aids

Turn OFF the ignition.
Disconnect the ignition control module 14-way connector.
Install an injector tester at any injector harness connector.
Turn ON the ignition, with the engine OFF.
Connect a test lamp to B+.
Repeatedly touch the test lamp to the 3X reference circuit at the ignition control module harness connector while observing the injector tester.

Does the injector tester blink?

Go to Step 8

Go to Step 5

Turn OFF the ignition.
Disconnect the PCM.
Turn ON the ignition, with the engine OFF.
Test for the following conditions:

-	An open 3X reference circuit

-	A 3X reference circuit that is shorted to ground

-	A 3X reference circuit that is shorted to voltage

If you find a problem, repair the condition as necessary. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 11

Go to Step 6

Inspect the 3X reference circuit for a poor terminal connection at the PCM.
If you find a problem, repair the condition as necessary. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 11

Go to Step 7

Inspect for the following conditions:

-	Incorrect harness routing near the secondary ignition components.

-	An ignition coil that is arcing to the wiring harness or to the ignition control module.

-	An ignition coils that has cracks, carbon tracking, or other signs of damage. Refer to Ignition Coil(s) Replacement .

-	Secondary ignition wires that are arcing to the wiring harness. Refer to Spark Plug Wire Harness Replacement in Engine Electrical.

If you find a problem, repair the condition as necessary.

Did you find and correct the condition?

Go to Step 11

Go to Step 10

Inspect for loose terminal connections at the ignition control module.
If you find a problem, repair the condition as necessary. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 11

Go to Step 9

Replace the ignition control module. Refer to Ignition Control Module Replacement .

Did you complete the replacement?

Go to Step 11

Important:: The replacement PCM must be programmed.

Refer to PCM Replacement/Programming .

Replace the PCM.

Did you complete the replacement?

Go to Step 11

Use a scan tool in order to clear the DTCs.
Operate the vehicle within the Conditions for Running the DTC, as specified in the supporting text.

Does the DTC reset?

Go to Step 2

System OK