Circuit Description
The ignition control (IC) module has independent power and ground circuits. The circuits between the IC module and the powertrain control module (PCM) consist of the following circuits:
| • | The IC timing signal |
| • | The IC timing control |
| • | The low-resolution engine speed signal |
| • | A low reference signal |
The ignition control (IC) module sends 3x signals to the powertrain control module (PCM). The IC module controls the timing advance during engine cranking. The timing advance changes to PCM control after the following actions:
| • | 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. |
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 Signal 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. |
Diagnostic Aids
| • | The engine will start and may run with IC module controlling spark timing. |
| • | If the condition is intermittent, refer to Intermittent Conditions . |
Step | Action | Values | Yes | No |
|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics | ||||
1 | Did you perform the Diagnostic System Check-Engine Controls? | -- | Go to Step 2 | |
2 |
Does the DTC fail this ignition? | -- | Go to Step 3 | Go to Intermittent Conditions |
3 |
Does the resistance measure less than the specified value? | 500 ohms | Go to Step 5 | Go to Step 4 |
4 |
Did you find and correct the condition? | -- | Go to Step 9 | Go to Step 6 |
5 | Test for poor terminal connections at the PCM. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 9 | Go to Step 8 |
6 | Test for poor terminal connections at the ignition control (IC) module. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 9 | Go to Step 7 |
7 | Replace the ignition control module. 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 |
Does the DTC run and pass? | -- | Got to Step 10 | Go to Step 2 |
10 | With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? | -- | System OK | |
