What Causes the ABS Light to Illuminate After a Vehicle Inspection?

[ArthurLynn]

There are various states of the ABS light being on, with different causes and solutions for each state. The details are as follows: State 1: ABS warning light stays on (most common). Cause 1: The ABS speed sensor's sensing part is covered by dirt, mud, or other contaminants, affecting its ability to detect the corresponding speed signal. This prevents the ABS computer from determining the vehicle speed and the wheel slip rate, thus failing to issue appropriate commands to adjust braking. Solution: Clean the dirt off the speed sensor and adjust the gap between the speed sensor and the signal ring to restore normal function. Cause 2: Loose connections between system lines or poor contact of the ABS relay lead to signal issues, causing system failure. Solution: Check the line connections and reconnect any loose parts. State 2: ABS warning light intermittently illuminates but turns off when accelerating. 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 light turns off. The ABS system's power supply voltage is too low, possibly due to poor terminal contact or grounding issues. Solution: Check the battery's specific gravity; inspect the charging system; 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 the grounding screw of the hydraulic valve body, then retighten it, cleaning the contact surface if necessary; check if the connector gap has widened; replace the ABS or ABS/ASR computer. State 4: ABS warning light illuminates during high-speed driving. Cause: During high-speed driving, the ABS computer detects a significant discrepancy between the rear and front wheel speed signals; incorrect tire or wheel rim specifications. Solution: Refer to the vehicle's tire and wheel rim specifications, as indicated on the label 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, push the brake switch linkage down fully with a finger, then release the brake pedal to complete the self-setting position; replace the brake light switch. 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, making it difficult for the driver to slow down or adjust the vehicle's path, posing significant safety risks.

[SanElliana]

After the vehicle inspection, the ABS light came on. I've experienced this quite a few times, mainly because the car gets moved around and tested during the inspection, which can make some components a bit unstable. The most common issue is with the wheel speed sensor. The sensor is located near the wheel and can get bumped, dirty, or loosened when the car is moved. If it malfunctions, the ABS system will trigger an error and the light will come on. Loose or corroded wiring connectors might also get tugged during the inspection. If the ABS control module temporarily fails, it can cause this issue. Sometimes, fuses can blow during the inspection's lighting tests. Don't underestimate this light—ABS failure affects braking safety, especially in rainy or snowy conditions where skidding is more likely. It's recommended to first try restarting the car to see if the light turns off. If not, head to a professional repair shop immediately to read the fault codes and get it fixed.