Circuit Description
Modules that are connected to the CAN serial data circuits monitor each other for serial data communications during normal vehicle operation. Operating information and commands are exchanged among the modules. the modules have prerecorded information about messages that are exchanged on the serial data circuits. The supervised and periodic messages are used by the receiving module as an availability, and state of health indicator from the transmitting module. If the engine control module (ECM) detects a message that indicates a loss of communication, invalid or corrupted serial data, or an active malfunction in the transmission control module (TCM), that requires ECM intervention, DTC P0701 sets.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P0701 Transmission Control System Performance
Conditions for Running the DTC
| • | The ignition is in any of the following positions: |
| - | Unlock |
| - | Accessory |
| - | Run |
| - | Crank |
| - | OFF, but the ECM has not powered down |
| • | The ignition 1 voltage is more than 9 Volts. |
| • | Depending on the ignition mode, an engine run time of more than 1-3 seconds is required for certain messages. |
| • | This DTC runs continuously within the enabling conditions. |
Conditions for Setting the DTC
| • | The TCM has an active malfunction and is requesting ECM intervention. |
| OR |
| • | Loss of communication between the ECM and the TCM. |
| OR |
| • | Invalid serial data between the ECM and the TCM. |
| OR |
| • | Loss of the state of health message between the ECM and the TCM. |
| OR |
| • | An active vehicle speed malfunction in the TCM. |
Action Taken When the DTC Sets
| • | The control module illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails. |
| • | The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame/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
| • | A module which loses power during the current ignition cycle, will have a Loss of Communication DTC set by the other modules that require information from the failed module. |
| • | If the TCM, using a faulty manifold absolute pressure (MAP) signal, calculates an invalid torque value, the TCM will command ECM intervention and set a DTC P0701. |
| • | If there is an active vehicle speed malfunction in the TCM, DTC P0701 will set. |
| • | If the ECMs ignition 1 voltage circuit, that is used to wake up the module is open, the TCM may set a DTC U2105 and request a limp-home mode, which will result in DTC P0701 also being set. |
Step | Action | Yes | No |
|---|---|---|---|
Schematic Reference: Engine Controls Schematics and LINK Connector End View Reference: Engine Controls Connector End Views or Engine Control Module Connector End Views | |||
1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | |
2 |
Does the scan tool communicate with the ECM? | Go to Step 3 | |
3 | Select the DTC Information for the body control module (BCM), on the scan tool. Does the scan tool display any DTCs which begin with a U? | Go to Step 4 | |
4 | Select the DTC Information for the ECM. Does the scan tool display DTC P0107 or DTC P0108? | Go to Step 5 | |
5 | Select the DTC Information for the ECM. Does the scan tool display DTC P0502 or DTC P0503? | Go to Step 6 | |
6 |
Did the DTC fail this ignition? | Go to Step 2 | Go to Step 7 |
7 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | System OK | |
