What does fault code ECM-U04028F mean?

Diagnostic fault code details for ECM-U04028F (Volvo S60 (2011–), Volvo S60 (2011–), Volvo S80 (2007–)). Repair service at OBD Tuning.

VOLVO

ECM-U04028F - Invalid Data Received from TCM. Bus Signal / Message Failures. Erratic

System

Engine Control Module (ECM)

Volvo models this fault code applies to

Applies to the following models:

6 models

S60 (2011–), S80 (2007–), V40 (2013–), V40 Cross Country (2013–), V60 (2011–), V70 (2008–)

Show models by year and engine (11)

What does this fault code mean?

The TCM keeps asking the engine control module for a set amount of torque. That torque can be adjusted through the air, which is slow, or through ignition timing, which is fast. The code is set when the torque signal from the TCM arrives with poor quality. Although the code is titled erratic, it concerns the quality of that torque signal.

Possible causes

Fault in the transmission control module (TCM), which should be checked first
Disturbances or breaks on the CAN network

What you can do

1Fix the codes in the transmission control module first. Troubleshooting is done there
2Check the CAN connectors between the engine control module and the transmission module for contact resistance and oxidation
3Look for disturbances on the CAN network, such as chafed wires or pinched areas. Use a multimeter to check that the wires have no break
4Clear the code only after the root fault is fixed, then road test the car to see whether it returns
5If the code comes back: have a workshop with diagnostic equipment check the transmission control module

Symptoms you may notice1

No noticeable symptoms for the driver

General guidance for car owners. Diagnosis on the car can point to a different cause.