GM Service Manual Online
For 1990-2009 cars only

Circuit Description

The engine control module (ECM) monitors the condition of the ignition relay control circuit. If the ECM senses excessive voltage on this circuit, DTC P0612 will set.

Conditions for Running the DTC

The ignition is ON.

Conditions for Setting the DTC

The feedback voltage does not match the output state.

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.

Diagnostic Aids

If the engine starts, the ignition relay control circuit is shorted to power intermittently.

Step

Action

Values

Yes

No

Schematic Reference: Engine Controls Schematics

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

1

Did you perform the Diagnostic System Check-Engine Controls?

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Go to Step 2

Go to Diagnostic System Check - Engine Controls

2

Attempt to start the engine.

Does the engine start?

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Go to Diagnostic Aids

Go to Step 3

3

  1. Turn OFF the ignition.
  2. Remove the ignition 1 relay using J 43244 Relay Puller Pliers.
  3. Disconnect the ECM connector containing the ignition 1 relay control circuit. Refer to Engine Control Module Replacement .
  4. Turn ON the ignition.
  5. Probe the ignition 1 relay control circuit with a test lamp connected to a good ground. Refer to Troubleshooting with a Test Lamp in Wiring Systems.

Does the test lamp illuminate?

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Go to Step 5

Go to Step 4

4

Using a DMM, measure the resistance of the coil circuit of the ignition 1 relay.

Does the resistance measure within the specified range?

60-80 ohms

Go to Step 7

Go to Step 6

5

Repair the short to battery or ignition voltage on the ignition 1 relay control circuit. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

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Go to Step 8

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6

Replace the ignition 1 relay.

Did you complete the replacement?

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Go to Step 8

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7

Replace the ECM. Refer to Engine Control Module Replacement .

Did you complete the replacement?

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Go to Step 8

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8

  1. Use a scan tool to clear the DTCs.
  2. Turn OFF the ignition for 30 seconds.
  3. Start the engine.
  4. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Does the DTC run and pass?

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Go to Step 9

Go to Step 2

9

With a scan tool, observe the stored information, Capture Info.

Does the scan tool display any DTCs that you have not diagnosed?

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Go to Diagnostic Trouble Code (DTC) List

System OK