OBD-II code · Network
U01B8 Lost Communication With Switch Input Module B
ECU lost communication with switch input module B (collects switch signals — windows, lights, etc.).
Is it safe to drive with U01B8?
Usually safe to drive in the short term. Get it diagnosed when convenient, sooner if the car drives differently.
Common causes
- Most likelyModule unpowered
- Less likelyGateway module routing CAN messages incorrectly
- Less likelyCAN terminating resistor (120 Ω) drifted out of spec
Symptoms
- Multiple warning lights may illuminate
- Affected modules may go into limp mode or shut down
- Specific functions inoperative depending on module
- Diagnostic tools may show communication faults
Repair at a glance
- Difficulty
- Medium
- DIY friendly
- Often, with basic tools
- Typical labour
- 0.5–3 h
- Emissions test
- Usually unaffected
- Parts involved
- Switch Input Module B, Can Bus
Related codes
- U01B7Lost Communication With Switch Input Module A
- U01B9Lost Communication With Switch Input Module C
- U01B5Lost Communication With Catalyst Heater Control Module
- U01B6Lost Communication With Fuel Heater Control Module
- U01BALost Communication With Park Lock/Pawl Control Module
- U01BBLost Communication With Battery Charger Control Module B
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.