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 medium resolution engine signal
    • The camshaft position signal
    • The low reference

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 ignition control (IC) timing signal circuit.

The ICM monitors the CKP sync signal when the engine is cranking. The CKP sync signal is passed from the CKP sensor to the ICM on the CKP sensor 2 signal circuit. The CKP sync signal is used to determine the correct cylinder pair and initiate the ignition coil firing sequence. The 18X reference pulses are passed from the CKP sensor to the ICM on the CKP sensor 1 circuit. The 18X reference pulses are used for fuel injection and ignition control. After the ICM receives both signals, the ICM passes the 18X and 3X reference signals to the PCM. The CMP and the CKP sensors share a 12 volt reference and low reference circuit. The CKP sensor consists of the following circuits:

    • A 12 volt reference
    • A low reference
    • A CKP sensor 1 signal
    • A CKP sensor 2 signal

Conditions for Running the DTC

The engine is running.

Conditions for Setting the DTC

The PCM does not monitor IC pulses while the IC mode spark advance is commanded.

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.

Test Description

The number below refers to the step number on the diagnostic table.

  1. This step determines if DTC P1362 is also set.

Step

Action

Values

Yes

No

Schematic Reference: Engine Controls Schematics

1

Did you perform the Diagnostic System Check-Engine Controls?

--

Go to Step 2

Go to Diagnostic System Check - Engine Controls

2

  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.
  3. With a scan tool, monitor the DTC information for DTC 1362 in the PCM.

Does the scan tool indicate that DTC 1362 is current?

--

Go to Step 6

Go to Step 3

3

  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, or within the parameters observed in the Freeze Frame/Failure Records.

Does the DTC fail this ignition?

--

Go to Step 4

Go to Intermittent Conditions

4

  1. Turn OFF the ignition.
  2. Disconnect the PCM.
  3. Turn ON the ignition.
  4. Probe the IC timing control circuit with a test lamp connected to ground.

Does the test lamp illuminate?

--

Go to Step 5

Go to Step 14

5

  1. Turn OFF the ignition.
  2. Leave the PCM disconnected.
  3. Disconnect the ICM connector.
  4. Turn ON the ignition.
  5. Probe the IC timing control circuit with a test lamp connected to ground.

Does the test lamp illuminate?

--

Go to Step 10

Go to Step 13

6

  1. Turn OFF the ignition.
  2. Disconnect the PCM.
  3. Disconnect the ignition control module.
  4. Probe the IC timing control circuit with a test lamp connected to battery positive voltage.

Does the test lamp illuminate?

--

Go to Step 11

Go to Step 7

7

  1. Leave the ignition OFF.
  2. Leave the PCM disconnected.
  3. Leave the ignition control module disconnected.
  4. Probe the IC timing signal circuit with a test lamp connected to battery positive voltage.

Does the test lamp illuminate?

--

Go to Step 12

Go to Step 8

8

  1. Leave the ignition OFF.
  2. Leave the PCM disconnected.
  3. Leave the ignition control module disconnected.
  4. Test for a short between the IC timing control and IC timing signal circuits. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 15

Go to Step 9

9

  1. Leave the ignition OFF.
  2. Reconnect the ICM.
  3. Leave the PCM disconnected.
  4. Turn ON the ignition.
  5. Connect a test lamp to the B+, and connect the DMM. Observe the voltage between the IC timing control circuit and a known good ground while probing the IC timing signal circuit with the test lamp.

Does the voltage toggle between the 2 indicated ranges?

20-40 mV to 150-250 mV

Go to Step 14

Go to Step 13

10

Repair the short to voltage in the IC timing control circuit. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 15

--

11

Repair the short to ground in the IC timing control circuit. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 15

--

12

Repair the short to ground in the IC timing signal circuit. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 15

--

13

Replace the ICM. Refer to Ignition Control Module Replacement .

Did you complete the replacement?

--

Go to Step 15

--

14

Replace the PCM. Refer to Powertrain Control Module Replacement .

Did you complete the replacement?

--

Go to Step 15

--

15

  1. Use the scan tool in order 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?

--

Go to Step 16

Go to Step 3

16

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

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

--

Go to Diagnostic Trouble Code (DTC) List

System OK