U01B5Lost Communication With Catalyst Heater Control Module
- Generic OBD-II code · Network
- Turns on the check-engine light
- Matters for the ITP
- Needs a drive cycle to confirm a fix
- How the car detects it
- Electric catalyst heating lets the converter start working within seconds of a cold start. Emitec's EMICAT disc runs on 12, 24 or 48 V and draws up to 300 A; in high-voltage hybrids Vitesco feeds it through a dedicated DC/DC converter, one form of the separate power electronics that make up a catalyst heater control module. U01B5 means the engine controller has lost contact with that unit, so it can neither command heating nor confirm it took place. No manufacturer documents the code publicly. Under CARB 1968.2, section (e)(2), OBD must verify that a heated catalyst hits its target temperature on schedule, and that check depends on the module. The driver sees a MIL; cold starts emit more and warm-up may run less smoothly; U04B6 covers invalid data from the unit.
- What you may notice
- MIL on
- Higher emissions and possibly rough running after a cold start
- Likely causes
- LikelyHeat or corrosion damage at the heater module connectors near the exhaust
- PossibleModule supply or high-current fuse open
- RareCatalyst heater control electronics faulty
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Hard · Usually a job for a workshop.Typical cost: €100 – €1,500
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.