GM Service Manual Online
For 1990-2009 cars only

Circuit Description

The ignition control module (ICM) has independent power and ground circuits. The circuits between the ICM and the powertrain control module (PCM) consists of the following circuits:

    • The ignition control (IC) timing signal
    • The IC timing control
    • The low resolution engine speed signal
    • The low reference signal

The ICM sends 3X signals to the PCM and controls the timing advance during engine cranking. The timing advance changes to PCM control after the following actions occur:

    • The PCM receives the second 3X signal
    • The PCM applies 5 volts to the IC timing signal circuit.
    • The timing advance switches to PCM control.

If the PCM detects an open in the IC timing control circuit, DTC P1351 sets.

Conditions for Running the DTC

The engine speed is greater than 600 RPM.

Conditions for Setting the DTC

    • The PCM detects an open in the IC timing control circuit.
    • The condition is present for 300 3X reference periods, 100 crankshaft revolutions.

Action Taken When the DTC Sets

    • The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
    • The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

Conditions for Clearing the MIL/DTC

    • The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
    • A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
    • A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
    • Clear the MIL and the DTC with a scan tool.

Step

Action

Values

Yes

No

Schematic Reference: Engine Controls Schematics

Connector End View Reference: Engine Controls Connector End Views or Powertrain Control Module Connector End Views

1

Did you perform the Diagnostic System Check-Engine Controls ?

--

Go to Step  2

Go to Diagnostic System Check - Engine Controls

2

  1. Observe the Freeze Frame/Failure Records for this DTC.
  2. Turn OFF the ignition for 30 seconds.
  3. Start the engine.
  4. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.

Did the DTC fail this ignition?

--

Go to Step 3

Go to Intermittent Conditions

3

  1. Disconnect the powertrain control module (PCM).
  2. Turn ON the ignition, with the engine OFF.
  3. Measure the resistance from the ignition control (IC) timing control circuit of the ignition control module (ICM) to the low reference circuit of the ICM with a DMM.

Is the resistance within the specified range?

100-600 ohms

Go to Step 6

Go to Step 4

4

  1. Turn OFF the ignition.
  2. Leave the PCM disconnected.
  3. Disconnect the ICM.
  4. Test the IC timing control circuit for an open. Refer to Circuit Testing in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 9

Go to Step 5

5

Test for an intermittent and poor connections at the ICM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 9

Go to Step 7

6

Test for an intermittent and poor connection at the PCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 9

Go to Step 8

7

Replace the ICM. Refer to Ignition Control Module Replacement .

Did you complete the replacement?

--

Go to Step 9

--

8

Replace the PCM. Refer to Powertrain Control Module Replacement .

Did you complete the replacement?

--

Go to Step 9

--

9

  1. Clear the DTCs with a scan tool.
  2. Turn OFF ignition for 30 seconds.
  3. Start the engine.
  4. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.

Did the DTC fail this ignition?

--

Go to Step 10

Go to Step 2

10

Observe the Capture Info with a scan tool.

Are there any DTCs that have not been diagnosed?

--

Go to Diagnostic Trouble Code (DTC) List

System OK