U01B7Lost Communication With Switch Input Module A
- Generic OBD-II code · Network
- How the car detects it
- A switch input module collects a group of buttons, for instance in a door trim, steering wheel or centre console, and sends their states to other units as network messages instead of wiring every switch on its own. A patent by Eaton describes the idea: a central unit queries every switch by its address and accepts only answers whose address and state are valid. U01B7 is set when module A stops responding, so the receiver, often the body controller, treats its buttons as unknown. Which switches belong to module A is up to each carmaker; no manufacturer documents this code publicly. Typically a whole group of buttons does nothing and their indicator lamps stay dark, while all other systems keep working. U04BA is the invalid-data code; modules B and C have U01B8 and U01B9.
- What you may notice
- A group of buttons without function
- Switch backlight or indicator lamps dark
- Likely causes
- LikelyLoose connector or broken wire at the switch panel
- PossibleLiquid spilled into the switch module
- RareSwitch input module A faulty
- Repair
- Medium · Often possible to do yourself.Typical cost: €0 – €400
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.