Lost Communication With "Door Control Module C"

Possible causes

• CommonBroken wires in the door loom where it crosses the hinge - these flex thousands of times and eventually fatigue
• CommonWater ingress into the door - a perished membrane or blocked drain soaks the module
• CommonLow battery voltage or a discharged battery, dropping modules off the bus
• CommonBlown fuse or corroded earth on the supply to door control module "C"
• CommonCorroded connector inside the door or under the seat
• PossibleFailed module or motor
• PossibleConnector disturbed during trim, seat, speaker or window work
• PossibleModule not coded to the vehicle after replacement

What you might notice

• Window, mirror, lock or seat on one side not working
• Everything on one door dead at once
• Function works intermittently, often depending on whether the door is open
• Central locking not working on one door
• Interior light or door-ajar warning wrong
• Occasionally a battery drain

What to check, in order

1. Open and close the door slowly while operating the affected function. If it works in one door position and not another, the fault is in the loom at the hinge - which is the most common cause of every code in this group.
2. Peel back the rubber boot between the door and the body and look at the wires inside. Broken strands are often visible, and the insulation can look perfect while the copper inside has failed.
3. Check for water inside the door. A perished plastic membrane or a blocked drain hole soaks the module and corrodes its connector.
4. Check battery voltage and state of charge. A weak or failing battery drops modules off the bus and sets lost-communication codes with no wiring fault at all.
5. Check the fuses and earths for door control module "C".
6. Note whether everything on that door failed together. That points to the loom or the module; a single function failing points to that motor or switch.
7. Check whether the connector was disturbed during recent trim, speaker or window work.