GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2000 🢒 GMC K Pickup - 4WD 🢒 Engine 🢒 Engine Controls - 7.4L 🢒 DTC P1345 Crankshaft Position (CKP)-Camshaft Position (CMP) Correlation

Object Number: 600798 Size: LF
VCM Connector End Views
Engine Controls Components
Engine Controls Schematics
OBD II Symbol Description Notice
Handling ESD Sensitive Parts Notice
Handling ESD Sensitive Parts Notice

Circuit Description

This diagnostic trouble code (DTC) monitors the crankshaft position (CKP) and the camshaft position (CMP) signals to determine if they are synchronized. If both signals are not observed by the control module within a narrow time window, the vehicle control module (VCM) will determine that an error has occurred.

Conditions for Running the DTC

The engine is running.

Conditions for Setting the DTC

The falling edge of the CMP sensor signal is more than 15 degrees out of phase with the falling edge of the CKP sensor.

Action Taken When the DTC Sets
    • The control module illuminates the malfunction indicator lamp (MIL) the first time the diagnostic runs and fails.
    • The control module will set the DTC and records the operating conditions at the time the diagnostic fails. The control module stores the failure information in the scan tools Freeze Frame/Failure Records.

Conditions for Clearing the MIL or DTC
    • The control module turns OFF the MIL after 3 consecutive drive trips when the test has run and passed.
    • A history DTC will clear if no fault conditions have been detected for 40 warm-up cycles. A warm-up cycle occurs when the coolant temperature has risen 22°C (40°F) from the startup coolant temperature and the engine coolant reaches a temperature that is more than 70°C (158°F) during the same ignition cycle.
    • Use a scan tool in order to clear the DTCs.

Diagnostic Aids

Check the following items:

    • A loose CMP sensor causing a variance in the sensor signal
    • Excessive free play in the timing chain and gear assembly
    • Incorrectly installed distributor--one tooth off in either advance or retard positions
    • A loose distributor rotor on the distributor shaft
    • A loose or missing distributor hold-down bolt

An intermittent may be caused by any of the following conditions:

    • A poor connection
    • Rubbed through wire insulation
    • A broken wire inside the insulation

Thoroughly inspect any circuitry that is suspected of causing the intermittent complaint. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

If a repair is necessary, refer to Wiring Repairs or Connector Repairs in Wiring Systems.

Test Description

The numbers below refer to the step numbers on the table.

  1. This test will determine if this DTC is intermittent.

    2.

  2. When the engine speed is raised to 2,000 RPM, the camshaft retard offset should not vary more than 2 degrees.

    3.

  3. If excessive pressure is used when performing this test, unintentional damage to the distributor shaft could result.

    4.

  4. If the distributor is one tooth off in either the advanced or retard positions the vehicle may run but 0 degree camshaft retard offset will not be obtained.

    5.

  5. If 0 degree cannot be obtained during this procedure, refer to Diagnostic Aids.

Step

Action

Values

Yes

No

1

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

--

Go to Step 2

Go to Powertrain On Board Diagnostic (OBD) System Check

2
  1. Install the scan tool.
  2. Start the engine.
  3. Use the scan tool in order to monitor the engine speed.

Does the engine speed fluctuate, up to twice the desired RPM?

--

Go to Step 3

Go to Step 4

3

Replace the crankshaft position sensor. Refer to Crankshaft Position Sensor Replacement .

Is the action complete?

--

Go to Step 10

--

4

Perform the camshaft retard offset test procedure as follows:

  1. Install the scan tool.
  2. Start the engine.

    3. Important: The camshaft retard reading will not be accurate below 1,000 RPM.

  3. Raise the engine speed to the first specified value.
  4. Monitor the camshaft retard with the scan tool.

Is the camshaft retard reading within the second specified value?

1,000 RPM

-2° to 2°

Go to Step 5

Go to Step 6

5

  1. Note the camshaft retard reading from the previous step.
  2. Raise the engine speed to the first specified value.

Does the camshaft retard reading change more than the second specified value?

2000 RPM

2°

Go to Step 6

Go to Diagnostic Aids

6

With the engine at operating temperature and the engine OFF, perform the following procedure:

  1. Remove the distributor cap.
  2. Grasp the distributor rotor and gently attempt to rotate the rotor.

Does the rotor turn on the distributor shaft?

--

Go to Step 9

Go to Step 7

7

  1. Inspect for proper installation of the distributor.
  2. Repair as necessary. Refer to Distributor Replacement in Engine Mechanical.

Did you find a problem?

--

Go to Step 10

Go to Step 8

8

Perform the camshaft retard offset adjustment procedure as follows:

  1. With the engine OFF, sightly loosen the distributor hold down bolt.
  2. Start the engine and raise the engine speed to 1,000 RPM.
  3. Using the scan tool, monitor the camshaft retard offset.
  4. Rotate the distributor as follows:
    5. • To compensate for a negative reading, rotate the distributor in the counterclockwise direction.
    • To compensate for a positive reading, rotate the distributor in the clockwise direction.
  5. Repeat step 4 until 0 degrees offset is obtained.
  6. When 0 degrees has been obtained, turn OFF the ignition and tighten the distributor hold down bolt.

Did you obtain 0 degrees camshaft retard?

--

Go to Step 10

Go to Diagnostic Aids

9

Replace the distributor. Refer to Distributor Replacement in Engine Electrical.

Is the action complete?

--

Go to Step 10

--

10
  1. Using the scan tool, clear the DTCs.
  2. Start the engine.
  3. Allow the engine to idle until the engine reaches normal operating temperature.
  4. Select DTC and the Specific DTC function.
  5. Enter the DTC number which was set.
  6. Operate the vehicle, with the Conditions for Setting this DTC, until the scan tool indicates the diagnostic Ran.

Does the scan tool indicate the diagnostic Passed?

--

Go to Step 11

Go to Step 2

11

Does the scan tool display any additional undiagnosed DTCs?

--

Go to the applicable DTC table

System OK