What it means
ABS pump motor supply B above expected range. Wiring faults of this kind typically come from chafing, water ingress at connector seals, or pin push-back — a wiggle test on the harness while the code is active often confirms the location.
At a glance
- Usually lights the ABS or stability-control warning light
- The engine or gearbox may go into limp mode
How it works
Supply voltage B powers the ABS pump motor, which the brake control module uses to regulate hydraulic pressure during ABS operation. C05A6 sets when the monitored supply B voltage is higher than expected, potentially from an overvoltage or a wire connected to battery positive unintentionally.
Common causes
Most likely first.
- Overvoltage
- Connector pins corroded - high contact resistance
- Supply wire pinched against B+ source
Symptoms
- ABS warning light on
- ESC/stability control deactivated
- Possible reduced brake assist
- Speedometer may behave erratically
How to diagnose it
- Read ABS codes and freeze-frame data to confirm the high supply B fault and note whether other power supply or charging faults are stored.
- Inspect the ABS pump motor supply B wiring and connector for corrosion, damaged pins, or wiring pinched against a battery-positive source.
- Check system voltage and related charging or power supply codes against the manufacturer's information to identify an overvoltage condition.
- Use the wiring diagram to test supply B for unintended battery voltage and inspect connector contact and harness condition.
- If the external circuit is sound, test the brake module's supply B monitoring and pump motor circuit using the manufacturer's procedure.
Common fixes
- Repair a charging or power supply fault causing overvoltage.
- Secure the connector and repair damaged terminals or seals in the supply B circuit.
- Repair a supply wire pinched against battery-positive wiring.
- Repair or replace the brake module or pump motor only if testing confirms an internal fault.
Can I keep driving?
ABS and stability control may be disabled, and the pump circuit may be at risk of further electrical damage if the overvoltage persists. Avoid high-speed driving and slippery roads, and stop if braking changes or charging-system warnings appear.
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.