U018ALost Communication With Headlamp Leveling Control Module B
- Generic OBD-II code · Network
- How the car detects it
- U018A covers headlamp leveling control module B. Cars with separate levelling electronics in each headlamp, or with a central controller plus lamp-side units, need a second address; U0181 is the first module. The electronics set the beam angle from ride-height sensor data so that load or pitch does not dazzle oncoming traffic, which LED and xenon lamps usually require. No manufacturer documents U018A publicly, and it appears neither in GM's U-code list nor in the NHTSA bulletin index. The trigger is the same as for other lost-communication codes in GM's description: a periodic message missing at 9-16 V supply. Beam height on one side may freeze or drop to a low default, a lighting warning is possible, the MIL stays off. U048B is invalid data from B.
- What you may notice
- One headlamp no longer adjusts its beam height
- Headlamp or lighting warning in the cluster
- Uneven or very low beam pattern
- Likely causes
- LikelyLevelling module B without power or ground
- PossibleCorroded connector at the headlamp from moisture
- PossibleBus line to the headlamp damaged after a front-end repair
- RareHeadlamp levelling module B faulty or not coded
- Repair
- Medium · Usually a job for a workshop.Typical cost: €60 – €900
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.