GM Service Manual Online
For 1990-2009 cars only

Refer to

Cell 20: Ignition Control


Object Number: 380917  Size: FS
Engine Controls Components
Powertrain Control Module Description
Cell 20: Fuel Control (VIN 1)
Cell 20: MIL and Data Link Connector (DLC)
OBDII Symbol Description Notice
Cell 10: PDM, SIR, C31, INJR, and A/C CLU Fuses
Powertrain Control Module Connector End Views
Power and Grounding Connector End Views
Power and Grounding Connector End Views
Handling ESD Sensitive Parts Notice
Handling ESD Sensitive Parts Notice
Handling ESD Sensitive Parts Notice
for a wiring diagram.

Circuit Description

The Ignition Control Module (ICM) sends signals that the PCM requires for fuel control and spark advance calculations. At the start of engine crank, the ICM controls spark advance (Bypass mode). When the second 3X reference pulse is recognized by the PCM, the PCM applies 5 volts to the Bypass circuit. The 5 volts on the Bypass circuit commands the ICM to switch spark advance to PCM control (IC mode). At this time, The ICM will remove the ground it has applied to the IC circuit. When the IC pulses are not grounded, the ICM can use the IC pulses to control spark advance. A short in the IC circuit or an open or short to ground in the Bypass circuit will cause the PCM to monitor no IC pulses after the PCM has switched the Bypass circuit ON. The PCM will set DTC P1361 under either of these conditions. The engine may be started but will run on Bypass mode timing.

Condition for Running the DTC

The engine is running.

Conditions for Setting the DTC

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

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

Check for the following conditions:

    • Poor connection at the PCM.
        Inspect harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal to wire connection.
    • Damaged harness.
        Inspect the wiring harness for damage. If the harness appears to be OK, disconnect the ICM, turn the ignition ON and observe a digital multimeter connected between the IC circuit and B+ while moving connectors and wiring harnesses related to the ICM. A change in voltage will indicate the location of the malfunction.

Reviewing the Fail Records vehicle mileage since the diagnostic test last failed may help determine how often the condition that caused the DTC to be set occurs. This may assist in diagnosing the condition.

DTC P1361 - IC Circuit Not Toggling

Step

Action

Value(s)

Yes

No

1

Was the Powertrain On Board Diagnostic (OBD) System Check performed?

--

Go to Step 2

Go to Powertrain On Board Diagnostic (OBD) System Check

2

Is DTC P1362 set also?

--

Go to Step 6

Go to Step 3

3

  1. Turn OFF the ignition.
  2. Disconnect the PCM.
  3. Turn ON the ignition with the engine OFF.
  4. Probe the IC circuit with a J 35616-200 test lamp to ground.

Is the test lamp ON?

--

Go to Step 4

Go to Step 13

4

  1. Turn OFF the ignition .
  2. Leave the PCM disconnected.
  3. Disconnect the Ignition Control Module connector.
  4. Turn ON the ignition with the engine OFF.
  5. Probe the IC circuit with a J 35616-200 test lamp to ground.

Is the test lamp ON?

--

Go to Step 5

Go to Step 12

5

Locate and repair the short to voltage in the IC circuit. Refer to Wiring Repairs .

Is action complete?

--

Go to Step 14

--

6

  1. Turn OFF the ignition.
  2. Disconnect the PCM.
  3. Disconnect the Ignition Control Module.
  4. Probe the IC circuit with a J 35616-200 test lamp to B+.

Is the test lamp ON?

--

Go to Step 7

Go to Step 8

7

Locate and repair the short to ground in the IC circuit. Refer to Wiring Repairs .

Is action complete?

--

Go to Step 14

--

8

  1. Leave the ignition OFF.
  2. Leave the PCM disconnected.
  3. Leave the Ignition Control Module disconnected.
  4. Probe the BYPASS circuit with a J 35616-200 test lamp to battery positive voltage.

Is the test lamp ON?

--

Go to Step 9

Go to Step 10

9

Locate and repair the short to ground in the BYPASS circuit. Refer to Wiring Repairs .

Is action complete?

--

Go to Step 14

--

10

  1. Leave the ignition OFF.
  2. Leave the PCM disconnected.
  3. Leave the Ignition Control Module disconnected.
  4. Check for a short between the IC and BYPASS circuits.
  5. If a problem is found, repair as necessary. Refer to Wiring Repairs .

Was a problem found?

--

Go to Step 14

Go to Step 11

11

  1. Leave the ignition OFF.
  2. Reconnect the Ignition Control Module.
  3. Leave the PCM disconnected.
  4. Turn ON the ignition switch.
  5. Using J 39200 DMM, observe the voltage between the IC and Reference Low circuits while probing the BYPASS circuit with a J 35616-200 test lamp to B+.

Does the voltage toggle between the two indicated ranges?

20-40 mV

150-250 mV

Go to Step 13

Go to Step 12

12

Replace the Ignition Control Module. Refer to Ignition Control Module Replacement .

Is action complete?

--

Go to Step 14

--

13

Important: Replacement PCM must be reprogrammed.

Refer to Powertrain Control Module Replacement/Programming .

Replace the PCM.

Is action complete?

--

Go to Step 14

--

14

Review and record scan tool Fail Records data.

Clear DTCs.

Operate the vehicle within Fail Records conditions.

Using the scan tool, monitor Specific DTC Info for DTC P1361.

Does the scan tool indicate DTC P1361 failed this ignition?

--

Go to Step 2

System OK