VOLVO
TCM-DF18 - Control module communication. Control module communication
System
Transmission Control Module (TCM)
Volvo models this fault code applies to
Applies to the following models:
2 modelsS40 (1996–2004), V40 (1996–2004)
Show models by year and engine (2)
What does this fault code mean?
The transmission control module (TCM) and the engine control module communicate over the CAN network with two signal wires, CAN H and CAN L. The code is set when the transmission control module detects an open circuit in the CAN wires. It is one of several codes for faults on the same wires, and this one covers an open circuit.
Possible causes
- Open circuit in the CAN wires
What you can do
- 1Read the code, clear it and road test the car to see whether it comes back
- 2With the ignition off, check the CAN wiring between the gearbox and the engine for breaks, chafing and loose connectors
- 3Use a multimeter to check that both CAN wires are intact along the whole run between the control modules
- 4Check the connectors at both control modules for contact resistance and oxidation
- 5Have a workshop check CAN communication with diagnostic equipment and replace a control module if the fault remains after the wiring has been checked
Symptoms you may notice1
- The automatic gearbox warning lamp flashes
General guidance for car owners. Diagnosis on the car can point to a different cause.