Lost Communication With Park Brake Control Module

Possible causes

• CommonLow battery voltage or a discharged battery, dropping modules off the bus
• CommonBlown fuse or corroded earth on the supply to the park brake control module
• CommonDamaged, chafed or corroded bus wiring
• CommonCorroded or water-ingressed connector at the module
• PossibleFailed module
• PossibleAnother module faulting and dragging the whole bus down
• PossibleModule not coded or configured after a previous repair or replacement

What you might notice

• ABS, stability control and traction control warning lights on
• Anti-lock braking inoperative - a wheel can lock under hard braking
• Stability and traction control inoperative
• Electronic park brake may not release or apply on vehicles that use one
• Speedometer occasionally affected, since wheel speed often comes from this module

What to check, in order

1. Drive gently and allow much more stopping distance than usual until this is repaired. Nothing about the pedal will feel different, which is exactly why it catches people out on the first hard stop.
2. Check battery voltage and state of charge before anything else. A weak or failing battery drops modules off the bus and sets lost-communication codes with no wiring fault at all - this is the single most common false lead in this whole family.
3. Check whether this code is current or historic. Lost-communication codes are routinely set by a flat battery, a jump start or a battery disconnection, and a historic code straight after one of those events usually records the event rather than a fault.
4. Check the fuses and earth points for the park brake control module. ABS modules draw heavily and their earths corrode.
5. Note how many U-codes are stored. Several at once points at battery, earth or bus wiring, not at several modules failing simultaneously.
6. Inspect the module connector for corrosion and water. ABS modules are usually mounted low in the engine bay where water collects.
7. Do not condemn the module until power, earth, bus wiring and battery condition have all been eliminated.