VOLVO
GDM-0001 - Speed signal. Faulty signal
System
Gas Distribution Module (GDM)
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 xenon lamp control module (GDM) registers a speed signal that stays at a value that is too high for a longer period. The cause can be an incorrect speed signal from the instrument panel, intermittent short circuits or loose wiring in the signal cable, or electrical interference. The headlamps are set to their lowest position.
Possible causes
- Incorrect vehicle speed signal from the instrument panel
- Intermittent short circuit or loose wiring in the signal cable from the instrument panel
- Electromagnetic interference (EMC)
What you can do
- 1First read the fault codes for the speed signal in the instrument panel and for the wheel sensors in the ABS module, and remedy them
- 2Check the cable connector to the xenon lamp control module (GDM) for contact resistance and oxidation
- 3Inspect the leads running to every module that is linked up, looking for breaks and loose contacts
- 4If you have diagnostic equipment: compare the speed value in live data with the speedometer during a road test
- 5Clear the fault code after the repair and check that it does not return
Symptoms you may notice1
- The headlamp motor does not respond
What the fault can affect1
- The headlamps are set to their lowest position
General guidance for car owners. Diagnosis on the car can point to a different cause.