What causes the ABS light to come on after wading through water?

[JuneFitz]

There are various states in which the ABS light may illuminate, with different causes and solutions for each state, as detailed below: State 1: ABS warning light remains constantly on (most common). Cause 1: The ABS wheel speed sensor's sensing area is covered by mud, sludge, or other contaminants, affecting the sensor's ability to detect the corresponding wheel speed signal. This prevents the ABS control unit from determining the vehicle speed and wheel slip rate, thus failing to issue appropriate commands to adjust braking. Solution: Clean the dirt from the wheel speed sensor and adjust the gap between the sensor and the tone ring to restore normal function. Cause 2: Loose connections in the system wiring or poor contact in the ABS relay lead to signal issues, causing system failure. Solution: Inspect wiring 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 engine speed increases, the voltage rises, and the ABS light turns off. This may also occur due to insufficient power supply voltage to the ABS system, such as 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 remains on after engine start and only turns off when the engine is turned off (IGFF). Cause: Poor grounding contact in the ABS hydraulic valve body; loose wiring connections in the ABS hydraulic valve body; ABS control unit malfunction. Solution: Loosen and retighten the grounding screw of the hydraulic valve body, cleaning the contact surface if necessary; check for enlarged gaps in connectors; replace the ABS or ABS/ASR control unit. State 4: ABS warning light illuminates during high-speed driving. Cause: During high-speed driving, the ABS control unit detects a significant discrepancy between 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 fuel tank cap label. 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 use a finger to push the brake switch linkage fully downward, then release the brake pedal to complete self-positioning; replace the brake light switch if necessary. If the ABS warning light is on, it is advisable to avoid continued 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.