U0128: Lost Communication With Park Brake Control Module
What to do
If the park brake is stuck on, do not try to force the car to move — the rear brakes are clamped by electric motors and dragging them will damage the brakes and possibly the actuators. It will need recovering, and usually on a flatbed rather than towed, because releasing these by hand is a workshop procedure.
If the park brake is stuck off, the car drives normally and you have no handbrake. On an automatic, park will hold it on the level, but do not rely on that on a slope — the park pawl is a small mechanism that was never meant to be the only thing holding the car. Park on level ground where you can, turn the wheels into the kerb, and leave it in park or in gear. On a manual there is nothing holding it at all, so leave it in gear.
One thing worth passing on to any garage: rear pads on an electric park brake cannot be fitted the old way. The caliper has to be retracted electronically with a scan tool first — winding it back by hand wrecks the actuator, which is an expensive and very common mistake.
What this code means
The electric park brake module has stopped being heard from. The general reasoning is at U0100.
An electric park brake is the same argument as shift-by-wire at P0820, applied to the thing a driver relies on when they leave the car. There is no lever and no cable: a switch sends a request, a module decides, and small electric motors on the rear calipers apply or release the brake. Every part of that chain is electrical, and on most vehicles there is no mechanical override at all.
So losing the module produces one of two problems, and which one depends on the state it was left in.
- Stuck applied, and the vehicle cannot be driven. It is also not straightforwardly recoverable: winding the caliper motors back by hand is a workshop procedure, so a car in this state usually needs a flatbed rather than a tow.
- Stuck released, and the vehicle has no park brake. On an automatic the transmission's park pawl will hold it on level ground, but a park pawl is not designed to be the only thing holding a car on a slope, and on a manual there is nothing at all.
One thing that is not obvious and is expensive to learn: rear brake pads on these systems cannot be changed the traditional way. The caliper piston is driven by a motor, so winding it back by hand damages the actuator — the module has to be put into a service mode with a scan tool first. That is worth knowing whenever this module is involved in a job, and it is a common and costly mistake.
Likely causes
Start here
- Failed power or earth supply to the module · moderate
- Corroded or loose connector · easy
- Damaged data bus wiring · moderate
- Blown fuse or failed supply · easy
Less common
- Water ingress into connector · moderate
- Faulty park brake control module · specialist
Symptoms
Components involved
Information, not instruction
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Community experience
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