Intermittent brake warning light and steady ABS light. Master cylinder is full and parking brake is off. Had a problem last fall with ABS and found rear caliper sticking, so I replaced all rear pads, rotors and calipers. Front brakes look good and I couldn’t find any loose connections on ABS sensors. Thinking possibility that master cylinder might be the problem, or maybe moisture in brake fluid, as it has been below freezing here in Wisconsin, but it hasn’t gone away now that its been a bit warmer.
Any other ideas?
@Glurkus, you should get the ABS codes read and post them.
ABS sensors routinely fail, even if the connection’s good and tight. The tone ring might be dirty, or the sensor might have an open circuit.
Moisture in the brake fluid should not cause any warning lights.
Very often the code goes away when you clean the wheelspeed sensors. You have to take the wheels off and hose them down with brake cleaner. While you’re there, inspect the ring on the shafts to make sure one isn’t cracked.
If the primary brake warning light comes on it’ll cause the ABS light to come on automatically. The ABS light is just warning you that it’s not going to function until it’s found out what is causing the primary brake warning light to come on.
My 05 Town and Country started with ABS light on. Using Autel al619 scan tool ($100 on Amazon) I scanned ABS codes and got U14C404 CAB Internal Failure. Research said this is a problem with ABS module. ABS light on doesn’t prevent me from getting inspection sticker in Massachusetts, so I did not fix this problem. Following year, brake warning light also came on in dash board. Can’t get sticker with brake warning light on. Scanned ABS codes again. Still had CAB Internal Failure and now also had Right front wheel speed signal failure, and Right front sensor circuit failure. Same codes for the left side. I could not clear the codes with the scan tool. This vehicle has “active” two-wire wheel speed sensors which means you cannot test the sensors with an ohm meter. They will show an open circuit. Before you test sensors, make sure the Tone Ring looks good. Use a small wrench to tap the teeth to remove rust and build up and scrape out the spaces between the teeth. Also make sure the bottom of the sensor is clean, then start test. To test the sensors leave the sensors connected to the harness and back probe the connector. Make sure your probes go in far enough to make a good connection. Turn ignition key to “on” position and ABS module will supply sensor with a reference voltage. With your voltmeter set to DC volts, you should see about 9 or 10 volts. Rotate the wheel very slowly so one at a time the teeth of the tone ring pass under the sensor. You should see the voltage change by about 1 volt up and down as you do this. If you are able to measure the reference voltage, but don’t see any change as you rotate the wheel, chances are you need new wheel speed sensors. I found them online at autoparts warehouse for $20 each. Very easy to replace. After replacing my front sensors and driving a short distance, both warning lights went out.
In 2005, my 2002 Town & Country starter displaying the ABS light as soon as they salted the roads. It was intermittent at first, then steady as we got into winter. The brakes worked fine, just not the ABS.
I wasn’t much concerned because my other car, a 2004 PT Cruiser didn’t have ABS (one of the reasons I bought it ) We has a bunch of Chevt Suburbans and Chevy Van chassis small buses where I drove school bus and there ABS systems were pitiful and actually caused a couple of low speed dry road accidents by preventing them from stopping.
Is soon as Spring came and I drove fast in a good rain, the ABS light went out until the salt season returned. That continued until I sold the van years later.