Circuit Description
The ignition control module (ICM) controls spark timing when the engine is cranking. During this Bypass mode of operation, the ICM triggers each ignition coil in the proper sequence at a pre-calibrated timing advance. The ICM is connected directly to the powertrain control module (PCM) and includes the following circuits:
| • | A low reference circuit |
| • | The low resolution engine speed signal circuit |
| • | The ignition control (IC) timing control circuit |
| • | The IC timing signal circuit |
When the PCM begins receiving the 3X reference pulses from the ICM and the engine starts, the PCM applies 5 volts to the IC timing signal circuit. This allows the ICM to switch to the IC mode of operation and spark advance to be controlled by the PCM. The PCM monitors the IC timing signal circuit for errors. If the PCM detects a fault, DTC P1350 sets.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P1350 Ignition Bypass Circuit
Conditions for Running the DTC
| • | The engine is running or cranking. |
| • | DTC P1350 runs continuously when the above condition is met. |
Conditions for Setting the DTC
The PCM detects a fault in the IC timing signal circuit for more than 9 seconds.
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. |
Step | Action | Values | Yes | No |
|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics Connector End View Reference: Engine Controls Connector End Views or Powertrain Control Module Connector End Views | ||||
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information |
2 |
Did the DTC fail this ignition? | -- | Go to Step 3 | Go to Intermittent Conditions |
3 |
Is the voltage more than the specified value? | 4.9 V | Go to Step 4 | Go to Step 5 |
4 | Is the voltage more than the specified value? | 6 V | Go to Step 6 | Go to Step 9 |
5 |
Does the test lamp illuminate? | -- | Go to Step 7 | Go to Step 8 |
6 | Test the IC timing signal circuit between the ICM and the powertrain control module (PCM) for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 13 | Go to Step 12 |
7 | Test the IC timing signal circuit between the ICM and the PCM for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 13 | Go to Step 12 |
8 | Test the IC timing signal circuit between the ICM and the PCM for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 13 | Go to Step 10 |
9 | Test for an intermittent and poor connections at the ICM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 13 | Go to Step 11 |
10 | Test for an intermittent and poor connection at the PCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 13 | Go to Step 12 |
11 | Replace the ICM. Refer to Ignition Control Module Replacement . Did you complete the replacement? | -- | Go to Step 13 | -- |
12 | Replace the PCM. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming. Did you complete the replacement? | -- | Go to Step 13 | -- |
13 |
Did the DTC fail this ignition? | -- | Go to Step 2 | Go to Step 14 |
14 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | -- | Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information | System OK |
