What does fault code TCM-0077 mean?

Diagnostic fault code details for TCM-0077 (Volvo C30 (2007–2013), Volvo C30 (2007–2013), Volvo C30 (2007–2013)). Repair service at OBD Tuning.

VOLVO

TCM-0077 - P-lock function. Signal too low

System

Transmission Control Module (TCM)

Volvo models this fault code applies to

Applies to the following models:

4 models

C30 (2007–2013), C70 (2006–2013), S40 (2004–2013), V50 (2004–2013)

Show models by year and engine (10)

What does this fault code mean?

The gear selector has an electrically controlled lock (shift-lock) that is meant to stop it being moved out of position P by accident. The transmission control module is connected directly to the lock by its own cable. The fault concerns that cable, which is short-circuited or has an open circuit, so the lock function does not work.

Possible causes

Connector or cable is damaged
Damaged gear selector module (GSM)

What you can do

1With the ignition on and the selector in N: move it without the brake (it should not move); then press the brake and move it again (it should now move)
2Read off the fault code, clear it and check whether it comes back
3Check the connector at the control module and the cable to the lock for loose contacts, oxidation and chafing; a multimeter can check for open circuits or shorts to ground
4Have a workshop check the gear selector module and the transmission control system; if no other fault is found, one of them may need replacing

Symptoms you may notice1

Gears can be changed, but the shift-lock does not work

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