What does it mean when the ABS light comes on in a Mercedes-Benz?
2 Answers
The ABS light can illuminate in various states, each indicating different fault causes and requiring distinct handling methods. Details are as follows: State 1: ABS warning light stays on (most common). Cause 1: The ABS wheel speed sensor's sensing part is covered by mud, sludge, or other contaminants, affecting the sensor's ability to detect the corresponding speed signal. This prevents the ABS computer from determining the vehicle speed and wheel slip rate, thus failing to issue appropriate commands to regulate braking. Solution: Clean the dirt off the wheel speed sensor and adjust the gap between the sensor and the signal ring to restore normal function. Cause 2: Loose connections between system circuits or poor contact of the ABS relay leads to signal issues, causing system failure. Solution: Check the circuit connections and reconnect any loose parts. State 2: ABS warning light intermittently illuminates but turns off during acceleration. Cause: When multiple vehicle electrical devices are in use, the battery voltage drops below 10.5V. As the engine speed increases and voltage rises, the ABS warning light turns off. This may also occur if the ABS system's power supply voltage is too low due to poor terminal contact or grounding issues. Solution: Check the battery's specific gravity, inspect the charging system, and examine the power supply (e.g., voltage relay or poor power contact). State 3: ABS warning light stays on after engine start and only turns off when the engine is turned off (IGFF). Cause: Poor grounding contact of the ABS hydraulic valve body; poor contact in the ABS hydraulic valve body's wiring connector; ABS computer malfunction. Solution: Loosen and then retighten the grounding screw of the hydraulic valve body, cleaning the contact surface if necessary. Check if the connector gap has widened. Replace the ABS or ABS/ASR computer if needed. State 4: ABS warning light illuminates during high-speed driving. Cause: At high speeds, the ABS computer detects a significant discrepancy between the rear and front wheel speed signals. This may also occur due to incorrect tire or wheel rim specifications. Solution: Refer to the vehicle's tire and wheel rim specifications, as indicated on the sticker near the fuel tank cap. State 5: ABS warning light intermittently illuminates. Cause: Improper adjustment of the brake light switch; poor internal contact in the brake light. Solution: With the engine running, press the brake pedal and push the brake switch linkage fully down with your fingers. Release the brake pedal to complete the self-setting position. Replace the brake light switch if necessary. If the ABS warning light is on, it is advised not to continue driving. An illuminated ABS light indicates a malfunction in the vehicle's anti-lock braking system. During emergency braking, if the wheels lock up, the vehicle may skid uncontrollably, preventing the driver from slowing down or adjusting the vehicle's trajectory, posing significant safety risks.
That day while driving my old Mercedes-Benz C-Class to work, the ABS yellow warning light suddenly popped up on the dashboard, giving me quite a scare. This indicator means there's a malfunction in the anti-lock braking system. I immediately pulled over to check and found that while the brakes still worked, the pedal felt unusually stiff. The dealership mechanic had mentioned last time that it could be due to wheel speed sensors being clogged with mud or a blown fuse. Driving in rainy conditions requires extra caution without ABS assistance, as emergency braking can easily cause tire lock-up and loss of control. I scheduled a repair appointment that same day. The mechanic used diagnostic equipment and found that the right front wheel sensor wiring had aged and short-circuited, costing over 500 yuan to replace the wiring. My advice is not to delay when you see this warning light – drive slowly to a repair shop for inspection as soon as possible.
