Circuit Description
Engine torque information is sent to the transmission control module (TCM) by the engine control module (ECM) through a communication network called GMLAN. Two circuits are used to communicate GMLAN data between the ECM and TCM. A fault in the GMLAN will not cause DTC P2637 to set by itself. If a GMLAN fault occurs, other DTCs will set before DTC P2637.
When the ECM sends the TCM an engine torque signal that is invalid, DTC P2637 will set. DTC P2637 is a type B DTC.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P2637 Transmission Torque Delivered Circuit
Conditions for Running the DTC
| • | The engine run time is greater than 5 seconds. |
| • | No other GMLAN errors are present. |
Conditions for Setting the DTC
Engine torque signal is below the lower limit, above the upper limit, or is an unreliable value for 2 seconds.
Action Taken When the DTC Sets
| • | The TCM requests the ECM to illuminate the malfunction indicator lamp (MIL) during the second consecutive trip in which the Conditions for Setting the DTC are met. |
| • | The TCM turns off the pressure control solenoid. When the pressure control solenoid is off, line pressure is at maximum. |
| • | The TCM freezes transmission adaptive functions. |
| • | The TCM inhibits Autograde braking and shift stabilization. |
| • | At the time of the first failure, the TCM records the operating conditions when the Conditions for Setting the DTC are met. The TCM stores this information as a Failure Record. |
| • | At the time of the second failure, the ECM records the operating conditions when the Conditions for Setting the DTC are met. The ECM stores this information as a Freeze Frame. |
| • | The TCM stores DTC P2637 in TCM history. |
Conditions for Clearing the DTC
| • | The ECM turns OFF the MIL after the sixth consecutive drive trip in which the TCM does not send a MIL illumination request. |
| • | A scan tool can clear the DTC. |
| • | The TCM clears the DTC from TCM history if the vehicle completes 40 warm-up cycles without a non 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 | Value(s) | Yes | No | ||||
|---|---|---|---|---|---|---|---|---|
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | |||||
2 |
Important:
Did you record any ECM Failure Records? | -- | Go to Step 3 | |||||
3 |
Did DTC P2637 reset? | -- | Go to Step 4 | Go to Intermittent Conditions | ||||
4 | Did any other DTCs set? | -- | Go to Step 5 | |||||
5 | Replace the TCM. Refer to Control Module References . Is the action complete? | -- | Go to Step 6 | -- | ||||
6 | Perform the following operation to verify the repair:
Has the test run and passed? | -- | Go to Step 7 | Go to Step 2 | ||||
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 |
