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 |
The IC module sends 3 X signals to the 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 3 X 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 is running.
Conditions for Setting the DTC
| • | The PCM detects an open circuit in the IC signal circuit. |
| • | The condition is present for 300 3 X reference periods, 106 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 in bypass mode 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 test lamp illuminate? | -- | Go to Step 6 | Go to Step 4 |
4 | Inspect the low reference circuit for an open. Did you find and correct the condition? | -- | Go to Step 6 | Go to Step 5 |
5 | Inspect for poor connections at the IC module. Did you find and correct the condition? | -- | Go to Step 6 | Go to Step 7 |
6 |
Does the resistance measure greater than the specified value? | 5,000 ohms | Go to Step 8 | Go to Step 7 |
7 |
Did you find and correct the condition? | -- | Go to Step 12 | Go to Step 9 |
8 | Inspect 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 12 | Go to Step 11 |
9 | Inspect for poor terminal connections at the IC module. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 12 | Go to Step 10 |
10 | Replace the IC module. Refer to Ignition Control Module Replacement . Did you complete the replacement? | -- | Go to Step 12 | -- |
11 | Replace the PCM. Refer to Powertrain Control Module Replacement . Did you complete the replacement? | -- | Go to Step 12 | -- |
12 |
Does the DTC run and pass? | -- | Go to Step 3 | Go to Step 13 |
13 | With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? | -- | System OK | |
