Circuit/System Testing

Ignition ON, attempt to establish communication with the TCM with a scan tool.
- If no communication with the TCM, refer to Scan Tool Does Not Communicate with Keyword Data Line for further diagnosis.
Ignition OFF, disconnect the harness connector of the TCM.
Ignition ON, verify that 1.5-3.4 volts is available between the CAN serial data low and the CAN serial data high circuits.
- If the voltage is not within the specified range, test the CAN communication circuits between the ECM and the TCM for an open, short to ground, or a short to voltage.
- If the circuits/connections test OK, replace the ECM.
If the circuits/connections test OK, replace the TCM.