What Causes the Trailer ABS Light to Illuminate?

[AllieMarie]

ABS light illumination can occur in various states, with different causes and solutions for each state, as detailed below: State 1: ABS warning light remains constantly illuminated (most common). Cause 1: The ABS speed sensor's sensing area is covered by dirt, mud, or other contaminants, affecting its ability to detect vehicle speed signals. This prevents the ABS computer from determining the speed and wheel slip rate, thus failing to issue appropriate commands for brake adjustment. Solution: Clean the contaminants from the speed sensor and adjust the gap between the speed sensor and the signal 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 the 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. The ABS warning light turns off as the engine speed increases and voltage rises. This can 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 remains illuminated after engine start and only turns off when the engine is turned off (IGFF). Cause: Poor grounding contact in the ABS hydraulic valve body, poor contact in the ABS hydraulic valve body wiring connector, or ABS computer malfunction. Solution: Loosen and retighten the grounding screw on the hydraulic valve body, cleaning the contact surface if necessary. Check for enlarged gaps in the connector and replace the ABS or ABS/ASR computer if needed. State 4: ABS warning light illuminates during high-speed driving. Cause: The ABS computer detects a significant discrepancy between rear and front wheel speed signals during high-speed driving. This can 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 label near the fuel tank cap. State 5: ABS warning light intermittently illuminates. Cause: Improper adjustment of the brake light switch or 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 the self-setting position. Replace the brake light switch if necessary. If the ABS warning light is illuminated, 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.