How to Diagnose a Fault When a Car Presents an ABS Fault Light

When a car is presenting an ABS fault light, start by plugging in your diagnostic service tool, select the ABS system and the correct vehicle make and / or model and read for any fault codes. It is worth noting that in this video, the traction control fault light is illuminated which will happen where traction control is fitted.

The video in the section below shows there is one fault code for the left hand front wheel speed sensor. Be aware that this might not be a faulty sensor, it could be faulty wiring. It is quite common for mechanics to take the reading from the diagnostic tool, replace the sensor and find the fault still exists because the wiring is faulty and not the part.

Having determined that the sensor needs to be replaced, disconnect the wheel speed sensor from the wiring harness. Now remove the sensor from its mounting. Clean the mounting face before fitting the replacement. Once fitted, reconnect the wiring harness. Clear the fault codes using the diagnostic service tool. Read the fault codes again to ensure no faults are found and that the system works well.