What it means
The primary brake system control module (ABS/ESC/iBooster) has requested the ECM to illuminate the MIL because of an emissions-relevant fault on its side — for example a regenerative braking fault on a hybrid that affects driveline torque flow. The original fault is in the brake module.
At a glance
- Usually lights the check-engine light
How it works
The brake system control module manages functions such as ABS and stability control and may also handle regenerative braking on some vehicles. This code means that module asked the engine control module to illuminate the check-engine light because it detected a fault it considers relevant to emissions or driveline operation; the underlying fault is reported by the brake module.
Common causes
Most likely first.
- Internal brake system control module fault
- Module power, ground, or wiring fault
- Communication fault between brake and engine control modules
Symptoms
- Check-engine light on
- ABS, brake, or stability-control warning light may also come on
- Brake or stability-control functions may be limited
How to diagnose it
- Scan the brake and engine control modules, record freeze-frame data, and retrieve the brake module's own fault codes because they identify the originating issue.
- Check whether ABS, brake, stability-control, or hybrid system warnings accompany the check-engine light.
- Inspect the brake module's power, ground, connectors, and wiring for loose connections, corrosion, or damage.
- Check communication and module status with a scan tool, noting any lost-message or voltage faults shared by the brake and engine modules.
- Follow the brake module codes to test the affected braking or regenerative-braking system against the manufacturer's specification.
Common fixes
- Repair a loose, corroded, or damaged brake module connector or harness.
- Repair the module's power or ground connection if testing identifies a fault.
- Correct the specific brake or regenerative-braking fault recorded by the brake module.
- Replace or reprogram the brake control module only if testing confirms its failure and the manufacturer's procedure calls for it.
Can I keep driving?
If the brake pedal feels abnormal or a red brake warning is on, stop safely and arrange assistance. If braking feels normal, drive cautiously and avoid relying on ABS, stability control, or regenerative braking until the brake module fault is diagnosed.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.