What it means
The control module monitors the circuit for ABS pump motor supply voltage B. It sets this code when the circuit is detected as open and the supply signal is unavailable.
At a glance
- Usually lights the ABS or stability-control warning light
- The engine or gearbox may go into limp mode
How it works
The ABS pump motor relies on supply voltage B to run the pump that helps regulate hydraulic pressure during ABS operation. C05A5 sets when the brake control module detects an open in the pump motor supply B circuit, leaving the supply signal unavailable.
Common causes
Most likely first.
- Fuse blown
- Pin pushed back out of connector body
- Cracked solder joint inside the module or sensor
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 supply B open and check for related pump motor or power supply faults.
- Inspect the ABS pump motor supply B connector and harness for a loose plug, pushed-back pin, corrosion, or a broken wire.
- Check the fuse and other supply points for circuit B specified in the vehicle wiring diagram, and investigate why any fuse has opened.
- With power isolated as specified by the manufacturer, test supply B circuit continuity and connector contact to locate the open.
- If the wiring and fuse are sound, test the pump motor and brake module supply B circuit using the manufacturer's procedure.
Common fixes
- Replace a failed fuse after checking for the cause of the failure.
- Reconnect the ABS pump motor supply B connector or repair a pushed-back terminal.
- Repair a broken wire or damaged connector in the supply B circuit.
- Repair or replace the pump motor or brake module only if testing confirms an internal fault.
Can I keep driving?
ABS and stability control may be unavailable because the pump may not operate, though the base brakes can still work. Drive cautiously only if normal braking is reliable, leave extra stopping distance, and stop if the brake pedal changes or a brake-system warning appears.
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.