U01B3Lost Communication With Brake Blending Actuator
- Generic OBD-II code · Network
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- How the car detects it
- The brake blending actuator divides each braking request between regeneration by the drive motor and the friction brakes, keeping pedal feel steady while the share shifts. Bosch states that its electromechanical iBooster, together with the ESP hev unit, can blend up to 0.3 g of deceleration. U01B3 is stored when the unit coordinating the brakes, normally the hybrid or brake controller, no longer hears this actuator. No manufacturer documents the code publicly. Lost recuperation raises energy use and, on hybrids, engine running time, and CARB 1968.2 expects hybrid systems to detect faults that disable regenerative braking. The friction brakes then do all the work: expect weaker recuperation, a changed pedal and a brake or hybrid warning. U04B4 is the invalid-data code.
- What you may notice
- Little or no regenerative braking
- Changed brake pedal feel
- Brake or hybrid system warning
- Likely causes
- LikelyCAN wiring or connector fault at the brake actuator
- PossibleActuator without supply voltage, often after low 12 V voltage
- RareBrake blending actuator 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 – €1,800
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.