Transmission Control Module (TCM) - 8HP45

U1401-IMPLAUSIBLE ENGINE SPEED SIGNAL RECEIVED

For a complete wiring diagram Refer to the Wiring Information.

Theory of Operation

The purpose of the diagnostic is to monitor the CAN BUS, the transmitted messages on the CAN BUS and the validity of the CAN signals. Several control units are connected to the CAN BUS which send their messages cyclically in a defined time window. The messages contain multiple signals representing vehicle information.

- When Monitored:
Continuously with the ignition on and voltage within a valid range.

No failure in CAN BUS monitoring.

No failure in CAN BUS or message monitoring.

- Set Condition:
When the TCM detects an incorrect CAN ID from the PCM.





Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. 8HP45 Pre-Diagnostic Troubleshooting Procedure

1. CHECK FOR BCM CAN BUS DTCS
1. With the scan tool, read BCM DTCs.

Are any BCM CAN BUS DTCs present?

Yes

- Testing and Inspection Perform the appropriate diagnostic procedure. Perform the diagnostic procedure for DTC U0001-CAN C BUS first.
- Perform the TRANSMISSION VERIFICATION TEST. Verification Tests.

No

- Go To 2

2. CHECK IF ENGINE DTCS ARE PRESENT
1. With the scan tool, read engine DTCs.

Are any engine DTCs present?

Yes

- Perform the appropriate diagnostic procedure.
- Perform the TRANSMISSION VERIFICATION TEST. Verification Tests.

No

- Using the schematics as a guide, check the Transmission Control Module A (TCMA) terminals for corrosion, damage or terminal push out. If no problems are found, replace and program the TCMA. Valve Body - Removal.
- Perform the TRANSMISSION VERIFICATION TEST. Verification Tests.