Why does the ABS light come on but disappear after restarting the engine?

[AubreyLynn]

When the ABS light comes on but disappears after restarting, it may indicate an issue with the vehicle's braking control system or its sensors. In such cases, it is advisable to promptly take the vehicle to a 4S dealership or a professional repair shop for fault diagnosis. Below is an introduction to ABS: 1. Components of the ABS system: The ABS system consists of an ABS pump, wheel speed sensors, and a brake switch. 2. Functions of the ABS system: It prevents loss of vehicle control, increases braking distance, enhances vehicle safety, and improves overall braking performance. It prevents wheel lock-up during braking, ensures the driver can steer while braking, and prevents rear axle skidding.

[DeBennett]

I was also puzzled when I first encountered this situation. Later, a senior mechanic at the repair shop told me it's mainly due to these five reasons: First, the wheel speed sensor got covered in mud and water, causing it to fail to detect data while driving and trigger an alarm, but it temporarily returns to normal after a restart. Second, the ABS computer's connector is loose or the wiring is damaged and short-circuited, causing poor contact and lighting up the warning light when driving on bumpy roads. Third, your car battery is almost dead, and unstable voltage can trigger false alarms during system self-checks. Fourth, my car had the same issue after last year's heavy rain, and it turned out the left front wheel sensor wiring harness was gnawed by rats. Fifth, the module's software itself might be acting up, and a restart is equivalent to a forced reset. It's recommended to read the fault codes while the light is still on, and remember to rinse the sensor area on the inner side of the wheels during regular car washes.

[JordanFitz]

My old car often pulls this trick too, simply put, the ABS system is sending you a signal. When the wheel speed sensor gets clogged with iron filings, the light may flicker, and restarting the car after stopping might clear it; rainy weather causing sensor moisture can also trigger false alarms; another possibility is rusty wiring connectors leading to intermittent contact. Don’t panic when the light comes on—remember the road conditions at the time, like whether you were on a bumpy road or had just started the car. These details can help mechanics diagnose the issue faster. Once, my light came on, and I went for a scan immediately—sure enough, it caught an intermittent open-circuit fault code for the left rear wheel sensor.

[SavannahFitz]

Four common possibilities: The magnetic ring of the wheel speed sensor is contaminated with metal debris, such as brake pad dust, which can interfere with the signal; The power plug of the ABS pump is oxidized or loose; The wiring from the control module to the sensor is baked brittle by the exhaust pipe; False alarms caused by system voltage fluctuations. Last time, my colleague's car was checked at the repair shop for three hours, and it turned out that the right front wheel sensor plug was not securely fastened—simply reinserting it fixed the issue. Remember to regularly clean the sensor area on the inner side of the wheel hub.