Top 10 ABS Fault Codes and How to Diagnose Them
Learn how to interpret, troubleshoot, and prevent the most common ABS fault codes that affect modern vehicles. A must-read for DIYers and auto technicians.
Why ABS Fault Codes Matter
The Anti-lock Braking System (ABS) is a vital component of modern vehicle safety. When ABS fault codes appear, your vehicle’s stability, traction, and stopping performance may be compromised. Identifying and resolving these codes quickly can prevent accidents and costly repairs.
Top 10 Most Common ABS Fault Codes
-
C0035 – Left Front Wheel Speed Sensor
Cause: Damaged sensor, corroded connector, broken tone ring
Fix: Replace sensor, clean connectors, inspect wiring
Prevention: Regular brake inspections, avoid deep water driving -
C0040 – Right Front Wheel Speed Sensor
Similar to C0035, often occurs in tandem. Requires similar diagnosis and repair. -
C0045 – Left Rear Wheel Speed Sensor
Often affected by debris or rust near the sensor ring. Cleaning may fix minor cases. -
C0050 – Right Rear Wheel Speed Sensor
Confirm signal loss via scan tool. Check rear hub assembly for damage. -
C0110 – ABS Pump Motor Circuit
Fix: Inspect ABS module and pump relay. May require pump replacement. -
C0121 – ABS Control Module Performance
Cause: Internal module failure
Fix: Module reprogramming or replacement -
C0265 – EBCM Relay Circuit
Caused by relay failure or corrosion on board. Reflow or replace EBCM. -
C0899 – Low Voltage to ABS Module
Fix: Check battery health, charging system, and grounds. -
C0800 – Control Module Power Circuit
Could indicate blown fuse or shorted wiring to ABS module. -
C1300 – ABS Solenoid Circuit Fault
Solenoids control pressure within ABS system. Fault may need valve body inspection.
How to Diagnose ABS Fault Codes
Proper diagnosis is essential to avoid unnecessary parts replacement. Follow these steps:
- Step 1: Use a professional OBD-II scanner with ABS capabilities, such as iCarsoft ABS tools.
- Step 2: Record all stored and pending codes.
- Step 3: Visually inspect wheel sensors, wiring harnesses, and connectors.
- Step 4: Perform live data analysis to compare wheel speed readings.
- Step 5: Clear codes and test drive to confirm repair effectiveness.
Preventing ABS Faults
Prevention starts with maintenance. Here are some key tips:
- Regularly clean wheel hubs and sensors, especially in winter regions.
- Avoid aggressive pressure washing near wheel bearings and tone rings.
- Replace brake fluid every 2-3 years to prevent internal corrosion.
- Inspect ABS wiring and grounds during routine service.
- Ensure battery and charging system are in good condition.
Recommended Tools
For accurate diagnosis and efficient repairs, consider these iCarsoft scanners:
- iCarsoft CR Pro+ – Multi-system scanner with ABS diagnostics
- iCarsoft POR V3.0 – Ideal for Porsche models with advanced ABS coverage
- iCarsoft MB V3.0 – ABS diagnostics for Mercedes-Benz vehicles
FAQ: ABS Fault Codes – Diagnosis, Fixes, and Safe Driving Tips
❓ Q1: What causes the ABS light to come on?
The ABS light can turn on due to issues like a faulty wheel speed sensor (e.g. code C0035), damaged wiring, low brake fluid, a bad ABS module, or corroded connectors. iCarsoft diagnostic tools help pinpoint the exact cause.
❓ Q2: Can I still drive my car if the ABS light is on?
Yes, you can drive short distances, but your anti-lock braking feature won’t function. It increases your risk of skidding, especially in wet or icy conditions. Immediate diagnosis is recommended.
❓ Q3: How do I reset the ABS light?
After fixing the underlying issue (like replacing a bad sensor), the light can often be reset using an OBD-II scanner like the iCarsoft POR V3.0. Some vehicles may reset automatically after a few drive cycles.
❓ Q4: What is the most common ABS fault code?
C0035 (Left Front Wheel Speed Sensor Circuit) and C0265 (Electronic Brake Control Module Relay Circuit) are among the most common. Both can be quickly diagnosed with a handheld scanner.
❓ Q5: How do I diagnose ABS problems without a scanner?
Look for symptoms like erratic braking, unusual noises, or inconsistent speed readings. While visual inspection helps, using a scanner is highly recommended for precise diagnostics.
❓ Q6: Which scanner is best for ABS code reading?
The iCarsoft CR Pro+ and POR V3.0 are excellent choices for ABS diagnostics. They offer manufacturer-specific code reading, real-time data, and one-click DTC reports.
❓ Q7: Can a low battery cause ABS light to come on?
Yes. A weak battery can cause low voltage in the ABS control module, triggering fault codes. Always check the battery and alternator output if the ABS warning appears intermittently.
❓ Q8: How can I prevent ABS issues in the future?
Regularly inspect sensors and wiring, keep your brake fluid clean and at the correct level, and avoid driving with damaged wheel bearings. Scheduled system scans with tools like iCarsoft can catch issues early.
