Worn brake pads or shoes that have triggered the wear sensor as designed; Damaged or chafed wiring harness at the wheel, often due to road debris or improper routing; Corroded or loose electrical connector at the brake wear sensor; Failed brake lining wear sensor itself, due to heat, contamination, or physical damage; Faulty ABS control module or body control module misinterpreting the sensor signal; Aftermarket brake pads installed without the correct wear sensor provision, causing an open circuit

DTC codes / C00xx · Brakes, steering and suspension / C004A

C004ABrake Lining Wear Sensor

Q: What does code C004A mean?

Brake Lining Wear Sensor. C004A is a generic chassis code indicating that the antilock brake system (ABS) module has detected a fault in a brake lining wear sensor circuit, which is used to monitor the thickness of the brake pads or shoes. The computer typically sets this code when the sensor signal is out of expected range, open, or shorted, preventing accurate wear reporting.

C004A is a generic chassis code indicating that the antilock brake system (ABS) module has detected a fault in a brake lining wear sensor circuit, which is used to monitor the thickness of the brake pads or shoes. The computer typically sets this code when the sensor signal is out of expected range, open, or shorted, preventing accurate wear reporting.

SystemChassis

Code typeGeneric (all makes)

SeverityLow

Fix difficultyIntermediate

AreaBrakes, steering and suspension

Symptoms you may notice

Illumination of the brake wear warning light or ABS light on the dashboard
Often no symptoms besides the warning light, as the braking system may still function normally
A message on the driver information center indicating brake pad wear or service required
In some cases, the ABS system may be disabled, but this is less common with a wear sensor fault alone
Intermittent warning light operation over bumps or when turning, indicating a loose connection

Common causes, most likely first

Worn brake pads or shoes that have triggered the wear sensor as designed
Damaged or chafed wiring harness at the wheel, often due to road debris or improper routing
Corroded or loose electrical connector at the brake wear sensor
Failed brake lining wear sensor itself, due to heat, contamination, or physical damage
Faulty ABS control module or body control module misinterpreting the sensor signal
Aftermarket brake pads installed without the correct wear sensor provision, causing an open circuit

How to diagnose and fix it

Inspect the brake pads and shoes at all wheels for actual wear, replacing them if they are at or below the minimum thickness specification.
Visually inspect the wear sensor wiring and connector at each wheel for damage, corrosion, or disconnection, repairing as needed.
Use a scan tool to read live data from the brake wear sensor circuit and compare it to the expected values to confirm the fault.
Check for continuity and resistance in the sensor circuit using a digital multimeter, following the manufacturer's test procedure.
If the sensor is faulty, replace it with a quality part that matches the original design and clear the code.
If the wiring and sensor are good, diagnose the ABS module or body control module for internal faults, which may require reprogramming or replacement.

Common Misdiagnosis of Brake Wear Sensor Codes

A common mistake is to replace the brake wear sensor without first checking the actual brake pad thickness, as the sensor may be functioning correctly and simply reporting worn pads.
The code can be set by a poor connection at the sensor connector that only acts up in wet or humid conditions, so a thorough wiggle test and dielectric grease application may be needed.
Some vehicles use a single wear sensor on one wheel only, so a code may not indicate wear on all pads; always inspect all four corners.
Aftermarket brake pads sometimes lack the wear sensor or use a different resistance value, causing a persistent code even with new pads; using OEM or OEM-equivalent pads is recommended.
The ABS module may store this code due to a low battery voltage event, so clearing the code after ensuring the battery is healthy can prevent unnecessary repairs.

Can I keep driving with C004A?

You can generally continue driving with this code because the brake wear sensor is a warning system and does not affect braking performance directly. However, you should inspect the brakes soon to avoid metal-to-metal contact and costly rotor damage.

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.