Circuit Description
To improve shift feel, the transmission control module (TCM) may request that the powertrain control module (PCM) reduce engine torque during shift events. When such a request is received, the PCM responds by retarding the base ignition timing and notifying the TCM that the request has succeeded. If the PCM is unable to comply with the request, the PCM sends the TCM a message that the request has failed.
The torque reduction request is sent to the PCM through a communication network called the controller area network (CAN). Two circuits are used to communicate CAN data between the PCM and TCM. A fault in the CAN will not cause DTC P2637 to set by itself. If a CAN fault occurs, other DTCs will set before DTC P2637.
When the TCM receives a torque reduction failure message from the PCM, then DTC P2637 will set. DTC P2637 is a type A DTC.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P2637 Transmission Torque Delivered Circuit
Conditions for Running the DTC
| • | The ignition voltage is 10.2-15.5 volts. |
| • | The engine speed is 400 RPM or greater. |
| • | No CAN DTC U0100. |
| • | Trans. Protection Mode is OFF. |
Conditions for Setting the DTC
The engine torque circuit signal is valid for 4 seconds.
Action Taken When the DTC Sets
| • | The TCM requests the PCM to illuminate the malfunction indicator lamp (MIL). |
| • | The TCM turns the trans. protection mode ON following the shift, if failure occurs during shift. |
| • | The transmission will operate in 5th gear in drive, 2nd gear in L. |
| • | The line pressure is at maximum. |
| • | The torque converter clutch (TCC) is disabled. |
| • | The TCM freezes the transmission adaptive functions. |
| • | The TCM sets engine torque to 270 N·m. |
| • | The TCM sets engine torque data to 300 N·m. |
| • | The PCM records the operating conditions when the Conditions for Setting the DTC are met. The PCM stores this information as Freeze Frame and Failure Records. |
| • | The TCM records the operating conditions when the Conditions for Setting the DTC are met. The TCM stores this information as Failure Records. |
| • | The TCM stores DTC P1781 in TCM history. |
Conditions for Clearing the MIL/DTC
| • | The PCM turns off the MIL after the third consecutive drive trip in which the TCM does not send a MIL illumination request. |
| • | A scan tool can clear the MIL/DTC. |
| • | The TCM clears the DTC from TCM history if the vehicle completes 40 warm-up cycles without an emission-related diagnostic fault occurring. |
| • | The TCM cancels the DTC default actions when the ignition is OFF long enough in order to power down the TCM. |
Step | Action | Yes | No | ||||
|---|---|---|---|---|---|---|---|
1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | |||||
2 |
Important:
Did you record any PCM Failure Records? | Go to Step 3 | |||||
3 |
Did DTC P2637 reset? | Go to Step 4 | Go to Testing for Intermittent Conditions and Poor Connections | ||||
4 | Did any other DTCs set? | Go to Step 5 | |||||
5 | Replace the PCM. Refer to Control Module References for replacement, setup, and programming. Is the action complete? | Go to Step 6 | -- | ||||
6 | Perform the following operation to verify the repair:
Does the DTC reset? | Go to Step 2 | Go to Step 7 | ||||
7 | With the scan tool, observe the stored information, capture info and DTC info. Does the scan tool display any DTCs that you have not diagnosed? | System OK |
