Circuit Description
The ignition control (IC) module sends signals that the powertrain control module (PCM) requires for fuel control and spark advance calculations. At the start of engine crank, the IC module controls spark advance. When the second 3X reference pulse is recognized by the PCM, the PCM applies 5 volts to the IC Timing Signal circuit, commanding the IC module to switch spark advance to PCM control .
Conditions for Running the DTC
The engine speed is more than 600 RPMs.
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 PCM illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails. |
| • | The PCM records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the PCM stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the PCM records the operating conditions at the time of the failure. |
| • | The PCM writes the conditions to the Freeze Frame and updates the Failure Records. |
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
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? | -- | Go 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 | |
