U0402 - INVALID DATA RECEIVED FROM TRANSMISSION CONTROL MODULE

The Transmission Control Module (TCM) provides transmission and component performance information to the ECM (Engine Control Module). The data is sent over a communication network known as a CAN (Local Area Network) bus. This network uses two circuits to carry out the data communication between the ECM and the TCM. It is important to mention that, a CAN bus failure will not cause the direct setting of code U0402, rather, if the network fails, it will set another DTC that relates to the problem.

When the U0402 OBDII diagnostic code is stored, it means that the ECM has received data from the TCM, which is not valid.

• Check Engine light stays on.
• Other fault codes stored.
• Problems when shifting gears.

The reasons for setting the U0402 OBD2 fault code are as follows:

• CAN bus network wiring may be faulty.
• The electrical connections of the communication circuits between the TCM and ECM may be damaged.
• The TCM or ECM could be defective.

The steps to resolve DTC U0402 OBDII code are:

• Consult the Technical Service Bulletins.
• With a scan tool it is necessary to verify if other DTCs are stored in addition to U0402. Pay attention to the ones that indicate TCM problems and diagnose them.
• Inspect and check the condition of the CAN bus network wiring between the TCM circuits and the ECM. If you discover high resistance or poor electrical connection, make the appropriate repairs.
• If after completing the above tests you still get the U0402 code, more complex checks need to be performed on the ECM.