U04B4Invalid Data Received From 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
- In hybrid and electric cars, brake blending decides how much of the requested deceleration the drive motor recovers as energy and how much the friction brakes supply; at low speed the hydraulic brakes take over completely. An electromechanical booster such as Bosch's iBooster, paired with a matching ESP, is rated for blending up to about 0.3 g of regenerative deceleration. U04B4 is stored when messages from the blending actuator arrive but their values are not credible. No manufacturer documents this code publicly. CARB 1968.2 requires hybrids to flag faults that disable or degrade regenerative braking, so a MIL is possible. U01B3 marks a silent actuator. Expect less regeneration, a changed pedal feel and a brake warning.
- What you may notice
- Brake system or hybrid warning light on
- Little or no regenerative braking, shorter range
- Brake pedal feels different or harder
- Likely causes
- PossibleBlending actuator or its pedal/position sensing faulty
- PossibleChassis bus wiring or connector fault
- PossibleBrake and drive controller software not matching after update or replacement
- RareLow 12 V supply affecting the actuator electronics
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Workshop only · Usually a job for a workshop.Typical cost: €150 – €2,000
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.