ABS Idiot Light



I have a 2001 Nissan Frontier. The ABS and Brake Idiot lights come on randomly. Sometimes on the highway, sometimes acceleating, sometimes braking, sometimes a bump in the road, sometimes at startup. Once on, they do not go off until the engine is shut off. I didn’t think this vehicle had ABS before this happened. I haven’t been able to engage a ABS braking action, light off or light on. Operation of the vehicle, acceleration and braking, with the lights on, seems normal. Items that may or may not be relevant, this started just after the transmission was changed. And continues after tires were replaced. My mechanic says there is one sensor associated with the ABS on this vehicle. Is this an indication of something I should be concerned about?


The BRAKE light is the one to really worry about. This is telling you there is an issue with the braking system that could be dangerous. The ABS light going on could be in response to the brake light, and could be shutting off the ABS system to prevent brake system damage. Get the BRAKE system checked out and fixed, then worry about the ABS.


I agree; unlike non abs brakes where failure may be symmetric and an all or none proposition; I’d be concerned about a malfunction in the worse possible moment with a braking malfunction that might not show up otherwise in normal operation.


Have you checked your brake fluid level?
Did you read your owner’s manual?


" My mechanic says there is one sensor associated with the ABS on this vehicle."

There are at least 4, one on each wheel. There is also a brake fluid pump and accumulator that have pressure sensors. Repairing these systems can get very expensive. Since you were unaware of it’s existence, you can probably live without it…If the light bothers you, remove it…


to tardis: The brake fluid was checked by the mechanic when we talked of this. What should I look for in the owner manual? I didn’t see any specific recommendations on the ABS light as I scanned it.

to Caddyman: There are no electrical wires to the wheel area. The mechanic and I looked for something that looked like a sensor and didn’t recognize any. What should I look for? As to the flip remark to remove it, well, I thought it was there for a reason and thought someone on this forum would know something relevant. Maybe someone besides you.


If you didn’t think the car had anti-lock brakes, and having an anti-lock light on just means that they will act exactly like non-antilock brakes, why are you upset when someone tells you to remove the light if it bothers you? The brake warning light should be investigated, however if you don’t have antilock brakes you have an electrical problem in the instrument cluster.


There’s only one wheel speed sensor on your vehicle and it’s located on the rear differential.

On most ABS’s, if the primary brake warning light comes on the ABS light automatically comes on. This is because the ABS won’t function if there’s a problem with the primary brake system. So once it’s determined what’s causing the primary brake warning light to come on and it’s corrected so the light no longer comes on, the ABS light should no longer come on.



I found your post interesting.

On my vehicle, the brake warning light is triggered by the level of fluid in the master cylinder, indicating a hydraulic leak or worn pads, or by the parking brake handle being pulled. It does not initiate the ABS warning light. The ABS system is its own seperate system, utilizing wheel speed sensors on all four corners with a computer driven modulator, its light triggered by a failure of the ABS action to affect the speed of the wheel upon which it’s acting.

My understanding was that my system was typical.


The brake warning light going on because the parking brake is engaged or the fluid level low will not turn on the ABS light. There are other sensors in the brake system that WILL turn on both lights. Some brake systems have a sensor on the master cylinder that will get triggered if there is a problem with the pressure differential between the two brake circuits. This problem should trigger the ABS light with the brake light.


I have a 2000 Camry and the brake light system is exactly as you describe. I checked this out in the factory manual wiring diagram. The brake light is only illuminated by the brake handle or the fluid is low in the reservoir. I was surprised at this since previous cars I had used a pressure differential switch to turn on the light.