What Causes the Indirect Tire Pressure Monitoring Fault and ABS Light to Illuminate?
2 Answers
ABS light illumination can occur in various states, each with different causes and solutions, 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 the corresponding speed signal. This prevents the ABS computer from determining the vehicle's speed and calculating the wheel slip rate, thus failing to issue appropriate commands to regulate braking. Solution: Clean the dirt from the speed sensor and adjust the gap between the sensor and the signal ring to restore normal function. Cause 2: Poor signal transmission due to loose connections between system wires or poor contact in the ABS relay, leading to system malfunction. Solution: Inspect wire 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, such as due to poor terminal contact or grounding issues. Solution: Check the battery's specific gravity, inspect the charging system, and verify 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, faulty wiring connections in the ABS hydraulic valve body, or ABS computer 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 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, or incorrect tire or wheel rim specifications. Solution: Refer to the vehicle's tire and wheel rim specifications, typically found 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 manually push the brake switch linkage down to its limit, then release the pedal to complete the self-setting process. Replace the brake light switch if necessary. If the ABS warning light is illuminated, it is advisable 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.
Last time I encountered a situation where both the tire pressure and ABS lights were on, a friend explained that it might be due to dirty or faulty wheel speed sensors, as these systems rely on them to monitor wheel speed. The sensors are located inside the wheels and are prone to getting clogged with mud or water or aging and breaking. It could also be uneven tire pressure, causing the sensors to mistakenly detect an issue, or poor wiring connections, such as loose plugs or worn wires. Low battery voltage or alternator failure can also trigger these warnings. I suggested first checking if the sensors are clean and if the tire pressure is consistent. If the lights remain on, it's best to quickly consult a professional technician to read the fault codes with diagnostic equipment to avoid brake failure while driving. Ignoring it is dangerous—if the ABS fails, accidents could occur on slippery roads. I've fixed similar issues before, and it took little time and saved money.
