P2638-TORQUE MANAGEMENT FEEDBACK SIGNAL PERFORMANCE
P2638-TORQUE MANAGEMENT FEEDBACK SIGNAL PERFORMANCE
For a complete wiring diagram, refer to the Wiring Information.
Theory of Operation
The Transmission Control Module (TCM) requests torque reductions over the CAN bus during a transmission shift to improve shift quality. The TCM verifies that the Powertrain Control Module (PCM) has performed the requested torque reduction by monitoring the response to the request. If the response is not within a specified tolerance, the TCM increments a counter, and if this counter reaches a threshold, the DTC sets.
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When Monitored:
Engine intervention active for at least 20 ms, no engine torque errors, engine torque demand is greater than 0.
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Set Condition:
Torque Reduction acknowledge bit - not set, no shift aborts, the error flag Torque Reduction Acknowledge is not set, Powertrain controller not supporting torque requests.
Possible Causes |
|---|
| CAN BUS CIRCUIT DTC PRESENT |
| TRANSMISSION CONTROL MODULE (TCM) |
| POWERTRAIN CONTROL MODULE (PCM) |
Always perform the NAG1 Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 28 - DTC-Based Diagnostics/MODULE, Transmission Control (TCM) - Standard Procedure).
1. CHECK FOR ENGINE DTC PRESENT
| 1. | With the scan tool, check engine DTCs. |
Are there any engine DTCs present?
Yes
- (Refer to 28 - DTC-Based Diagnostics/MODULE, Transmission Control (TCM) - Diagnosis and Testing) and perform the appropriate diagnostic procedure.
- Perform the NAG1 TRANSMISSION VERIFICATION TEST. (Refer to 28 - DTC-Based Diagnostics/MODULE, Transmission Control (TCM) - Standard Procedure).
No
- Go To 2
| 1. | With the scan tool, check for any CAN bus DTCs or a sign of a CAN bus failure. |
Are there any CAN bus DTCs present in any module other than the TCM or an overall indication of a CAN bus communication problem?
Yes
- This is an indication of a CAN bus communication problem. Depending on the DTC, refer to DTC Based Diagnostics and Non DTC Based Diagnostics for diagnostic procedures and other possible causes.
- Perform the NAG1 TRANSMISSION VERIFICATION TEST. (Refer to 28 - DTC-Based Diagnostics/MODULE, Transmission Control (TCM) - Standard Procedure).
No
- Go To 3
| 1. | Turn the ignition off to the lock position. |
| 2. | Replace and program the Powertrain Control Module in accordance with the Service Information. |
| 3. | With the scan tool, record the Environmental Data and erase Transmission DTCs. |
| NOTE: | If the TCM detects and stores a DTC, the TCM also stores the vehicles operating conditions under which the DTC originally set and is located in scan tool under Environmental Data. Before erasing any stored DTCs, record any available data to assist in duplicating the conditions in which the DTC originally set. |
| 4. | Using the Environmental Data recorded earlier, test drive the vehicle while trying to duplicate the conditions in which the DTC originally set. |
| 5. | With the scan tool, read Transmission DTCs. |
Did the DTC P2638-TORQUE MANAGEMENT FEEDBACK SIGNAL PERFORMANCE reset?
Yes
- Using the schematics as a guide, check the Transmission Control Module (TCM) terminals for corrosion, damage, or terminal push out. Pay particular attention to all power and ground circuits. If no problems are found, replace the TCM in accordance with the Service Information.
- Perform the NAG1 TRANSMISSION VERIFICATION TEST. (Refer to 28 - DTC-Based Diagnostics/MODULE, Transmission Control (TCM) - Standard Procedure).
No
- Test Complete.
- Perform the NAG1 TRANSMISSION VERIFICATION TEST. (Refer to 28 - DTC-Based Diagnostics/MODULE, Transmission Control (TCM) - Standard Procedure).