ABS light is on
Updated: 2026-11-14
The wheel speed sensor is the usual culprit — excess air gap, dirt, a damaged tone ring. The service brakes still work, but ABS is disabled — on a slippery surface you will need to brake more carefully. The code names the axle and side directly.
How to approach it
The ABS lamp means anti-lock braking is not working, but the normal brakes should still work. First check whether a brake or pressure lamp is lit with it, and record all the brake-system codes. If a red brake lamp is also on, do not drive until the pressure is understood. The cause is most often a wheel sensor or the ABS unit power, so check the wheel connectors first.
The reference does not mark any code in this group as a reason to stop.
These codes usually come with it: SPN 789, SPN 790, SPN 791, SPN 792, SPN 793.
Other codes for this system
- SPN 789ABS Wheel Speed Sensor, Axle 1, Left
- SPN 790ABS Wheel Speed Sensor, Axle 1, Right
- SPN 791ABS Wheel Speed Sensor, Axle 2, Left
- SPN 792ABS Wheel Speed Sensor, Axle 2, Right
- SPN 793ABS Wheel Speed Sensor, Axle 3, Left
- SPN 794ABS Wheel Speed Sensor, Axle 3, Right
- SPN 795ABS Pressure Modulator Valve, Axle 1, Left
- SPN 796ABS Pressure Modulator Valve, Axle 1, Right
- SPN 797ABS Pressure Modulator Valve, Axle 2, Left
- SPN 798ABS Pressure Modulator Valve, Axle 2, Right
- SPN 799ABS Pressure Modulator Valve, Axle 3, Left
- SPN 800ABS Pressure Modulator Valve, Axle 3, Right
What happens if you keep driving
Part of the brake circuit or ABS/EBS is out of service. The pedal may still feel normal — until the first emergency stop or descent.
Next comes longer stopping distance, a skid on a slick surface, failure on a long downgrade. This is the case where "I will take it slow" does not work.
What to check on the spot
Let the air system build to working pressure and listen for leaks. Don’t drive with faulty brakes.
Can I keep driving
The answer depends on the code, not the light. A yellow light is a warning; a red one means do not move. But even under a yellow light there are faults that require stopping right away — low oil pressure, overheating, lost brake pressure. Enter the code — the reference will tell you plainly whether to keep driving or stop.
Know the code number? Type it into the search — or paste the whole list from the scanner and we will show which fault is the real one.