VOLVO
ECM-A640 - Transmission control module (TCM). Signal missing
System
Engine Control Module (ECM)
Volvo models this fault code applies to
Applies to the following models:
3 modelsC30 (2007–2013), S40 (2004–2013), V50 (2004–2013)
What does this fault code mean?
The engine control module receives information on torque loss in the gearbox from the transmission control module (TCM) over CAN. If that signal is missing or faulty, the code is set. The fault may therefore lie in the transmission control module or in the communication with it, and the car's running can then be affected.
Possible causes
- A fault in the transmission control module (TCM)
What you can do
- 1Read the fault codes in the transmission control module (TCM) first, then in the central electronic module (CEM)
- 2The faults in the transmission control module and the CAN-related codes in the CEM must be remedied before this code is cleared
- 3Check the connectors and CAN wiring to the transmission control module for open circuits, chafing and oxidation
- 4Clear the fault code after the repair and road test the car to see whether the symptoms return
Symptoms you may notice2
- Poor performance
- Hesitation, surging or jerky running at a steady speed
General guidance for car owners. Diagnosis on the car can point to a different cause.