OBD-II code · Network
U0242 Lost Communication With Headlamp Control Module B
ECU lost communication with the headlamp control module B (matrix LED, adaptive headlights). A communication loss with this module breaks any function relying on its data — diagnostic tools may show 'no response' and dependent modules can fall into limp mode.
Is it safe to drive with U0242?
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
- Best left to a mechanic
- Typical labour
- 0.5–4 h
- Emissions test
- Usually unaffected
- Parts involved
- Headlamp Module B, Can Bus
Related codes
- U0241Lost Communication With Headlamp Control Module A
- U023ELost Communication With Front Distance Range Sensor - Right
- U0240Lost Communication With Entrapment Control Module B
- U0243Lost Communication With Parking Assist Control Module B
- U0244Lost Communication With Running Board Control Module A
- U0245Lost Communication With Entertainment Control Module - Front
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.