Faulty voltage regulator in the alternator causing overcharging; Corroded, damaged, or shorted wiring in the ABS pump motor supply circuit; Poor ground connection for the ABS module or pump motor; Failed ABS pump motor (internal short or resistance out of specification); Defective ABS control module; Blown fuse or faulty relay in the pump motor circuit (though less likely to cause high voltage); Water intrusion or contamination in the ABS connector

DTC codes / C05xx · Brakes, steering and suspension / C055A

C055AABS Pump Motor Supply Voltage Circuit A High

Q: What does code C055A mean?

ABS Pump Motor Supply Voltage Circuit A High. C055A indicates that the anti-lock braking system (ABS) control module has detected an abnormally high voltage on the power supply circuit for the ABS pump motor, specifically on circuit A. The module monitors the voltage feed to the pump motor and sets this code when the signal exceeds the expected range, which can be caused by a charging system fault, wiring issue, or internal module problem.

C055A indicates that the anti-lock braking system (ABS) control module has detected an abnormally high voltage on the power supply circuit for the ABS pump motor, specifically on circuit A. The module monitors the voltage feed to the pump motor and sets this code when the signal exceeds the expected range, which can be caused by a charging system fault, wiring issue, or internal module problem.

SystemChassis

Code typeGeneric (all makes)

SeverityMedium

Fix difficultyIntermediate

AreaBrakes, steering and suspension

Symptoms you may notice

ABS warning light illuminated on the dashboard
Traction control or stability control warning light may also be on
Often no symptoms besides the warning light
ABS may be disabled, leading to increased stopping distances in slippery conditions
In rare cases, the pump motor may run continuously or stay off, affecting brake assist
Other electrical systems may show erratic behavior if the cause is a charging system overvoltage

Common causes, most likely first

Faulty voltage regulator in the alternator causing overcharging
Corroded, damaged, or shorted wiring in the ABS pump motor supply circuit
Poor ground connection for the ABS module or pump motor
Failed ABS pump motor (internal short or resistance out of specification)
Defective ABS control module
Blown fuse or faulty relay in the pump motor circuit (though less likely to cause high voltage)
Water intrusion or contamination in the ABS connector

How to diagnose and fix it

Use a scan tool to retrieve all codes and verify C055A is current; clear codes and test-drive to see if it returns.
Check battery voltage and charging system output with a multimeter; ensure voltage is within 13.5–14.5 volts with the engine running.
Inspect the ABS pump motor supply circuit wiring for damage, corrosion, or loose connections; repair as needed.
Test the ABS pump motor relay and fuse; replace if faulty.
Measure resistance and voltage drop across the pump motor and ground circuit to identify excessive resistance or shorts.
If all external checks pass, test the ABS control module and pump motor according to manufacturer procedures; replace faulty components.
After repairs, clear codes and perform a road test to confirm the ABS system operates correctly and the code does not reset.

Overvoltage Faults Often Misdiagnosed

A high voltage code on the ABS pump motor circuit is frequently caused by a failing alternator voltage regulator, not the ABS system itself, so always check charging system voltage first.
Corroded ground connections can cause voltage spikes that the module interprets as high supply voltage, so inspect and clean grounds before replacing expensive ABS components.
Some vehicles set this code intermittently due to a weak battery that causes the alternator to overcharge; load-test the battery as part of diagnosis.
The code may be stored in history without an active warning light if the overvoltage event was brief, so do not replace parts based solely on a stored code without verifying current data.
Aftermarket accessories or improper jump-starting can introduce voltage spikes that trigger this code, so ask the driver about recent electrical work or jump starts.

Can I keep driving with C055A?

If the ABS warning light is on, the ABS system may be disabled, which can increase stopping distances in emergency situations. Avoid driving in slippery conditions or at high speeds until the fault is repaired, and do not continue driving if the brake pedal feels abnormal or the battery/charging warning light is also on.

Tools that help

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Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.