Circuit Description
The transmission control module (TCM) malfunction indicator lamp (MIL) request circuit signals the powertrain control module (PCM) that the TCM is requesting MIL illumination.
Conditions for Running the DTC
The ignition is ON.
Conditions for Setting the DTC
The PCM is detecting an incorrect voltage level on the TCM MIL request circuit.
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 References: Automatic Transmission Controls Schematics in Automatic Transmission-Allison | ||||
1 | Did you perform the Diagnostic System Check-Engine Controls? | -- | Go to Step 2 | |
2 | Connect a scan tool. Did P1781 fail this ignition? | -- | Go to Step 4 | Go to Step 3 |
3 |
Does the DTC fail this ignition? | -- | Go to Step 4 | Go to Intermittent Conditions |
4 |
Does the voltage measure near the specified value? | B+ | Go to Step 5 | Go to Step 6 |
5 | Test the TCM MIL request circuit for a short to voltage. Repair as necessary. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct a condition? | -- | Go to Step 12 | Go to Step 7 |
6 | Test the TCM MIL request circuit for an open. Repair as necessary. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct a condition? | -- | Go to Step 12 | Go to Step 7 |
7 |
Does DTC P0700 set, not setting P1781? | -- | Go to Step 8 | Go to Step 10 |
8 | Test the TCM connectors for a bad connection. Refer to Circuit Testing and Connector Repairs in Wiring Systems. Did you find and correct a condition? | -- | Go to Step 12 | Go to Step 9 |
9 | Replace the TCM. Refer to Transmission Control Module Replacement in Automatic Transmission-Allison. Did you complete the replacement? | -- | Go to Step 12 | -- |
10 | Test the PCM connectors for a bad connection. Refer to Circuit Testing and Connector Repairs in Wiring Systems. Did you find and correct a condition? | -- | Go to Step 12 | Go to Step 11 |
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 13 | Go to Step 2 |
13 | Observe the stored information, Capture Info with a scan tool. Does the scan tool display any DTCs that you have not diagnosed? | -- | System OK | |
