How to Troubleshoot When the Citroen ABS Light Comes On?

[McDaniela]

ABS light illumination can indicate various conditions, each with different causes and solutions as follows: Condition 1: ABS warning light stays constantly on (most common). Cause 1: The ABS wheel speed sensor's sensing area is covered by mud, sludge, or other contaminants, affecting its ability to detect speed signals. This prevents the ABS control unit from determining vehicle speed or wheel slip rate, thus failing to issue proper braking commands. Solution: Clean the wheel speed sensor and adjust its clearance with the tone ring to restore normal function. Cause 2: Loose system wiring connections or poor ABS relay contact causing signal issues. Solution: Inspect wiring connections and resecure any loose parts. Condition 2: ABS warning light intermittently illuminates but turns off during acceleration. Cause: Battery voltage drops below 10.5V when multiple electrical components are used. The light extinguishes when engine RPM increases and voltage rises. Possible low voltage supply to ABS system due to poor terminal contact or grounding issues. Solution: Check battery specific gravity; inspect charging system; examine power supply (e.g., voltage relay or poor power contacts). Condition 3: ABS light remains on after engine start until ignition is turned off. Cause: Poor grounding of ABS hydraulic valve body; faulty wiring connections at valve body; ABS control unit malfunction. Solution: Loosen then retighten valve body ground screw, cleaning contact surfaces if needed; check for enlarged connector gaps; replace ABS or ABS/ASR control unit. Condition 4: ABS light activates during high-speed driving. Cause: ABS control unit detects excessive speed difference between front and rear wheels; incorrect tire or wheel rim specifications. Solution: Verify proper tire/rim specifications per vehicle requirements (refer to fuel filler cap label). Condition 5: Intermittent ABS warning light activation. Cause: Improper brake light switch adjustment; internal switch contact issues. Solution: With engine running, fully depress brake pedal while manually pushing switch lever downward, then release pedal to reset position; replace brake light switch if needed. Important: When the ABS light is illuminated, avoid continued driving as it indicates anti-lock braking system failure. During emergency braking, wheel lock-up may cause loss of vehicle control, preventing proper deceleration or trajectory adjustment, creating significant safety risks.