ABS yellow light came on a lot today......

tbirdsc35th

Registered User
I am sorry this is a repeat question from a while ago. I am no ABS expert by any means and many of you have been there before. Today I was running around town most of the afternoon. For long stretches of time, the yellow ABS light would come on and remain on for most of the time I was on the road. It didn't do it ALL the time but very often. Sometimes it just went out by itself. It always went off if I started the car and just sat there. Braking was normal and not a problem. Fluid is fine. The shop manual mentions as possible problems:
- main power relay
- fluid level indicator switch
- pressure warning switch
- actuator or actuator ground strap (is this the accumulator?)
- wheel sensors
- solenoid valve block unit
- pump motor relay

I am assuming that under normal conditions, when the ABS kicks in the yellow light comes on. I don't hear a pump going under the hood so I tend to discount that avenue. Has anyone encountered any other problems that I can add to the list of checking? I am so strapped for time lately, I was just hoping to get input from you guys who have been there to help me check these things out.

Thanks and sorry for the long post.

Have a great week and my best to all.
 
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Actuator ground strap is a ground cable that bolts onto the front of the brake booster unit. Make sure it's not corroded or broken.

Chances are, if your braking seems normal, your pump is working okay.

I'd guess a faulty wheel sensor. Have a peek and see if you picked up a stick and it mangled the wires going to one of the encoder rings (wheel speed sensors)

Lift up on your parking brake. Does the red BRAKE light come on? If not, maybe the bulb is burnt out and the car is trying to tell you something else but can't.
 
Katoom, Bingo. Finally got under the car today and looked at everything. The passenger side half shaft seal is leaking and differential fluid is all over that side ABS sensor wheel and pickup. I cleaned it all off and the ABS light sequence is now normal. I don't know if this is critical but it isn't a bad leak. Anyway just wanted to pass this along in case it happens to anyone else.

Have a great weekend all.
 
Wow. I didn't think that a major oil leak would cause that....but I guess if it fixed it, then thats great.
I'd like to share with some of you a little maintenance tip.
Once a year I pull the wheels off and I clean the ABS encoder wheels free of dirt with a small wire brush, or wash them.
The rear usually gets some oil on there from the diff and the dirt is attracted to that. If the dirt isn'r cleaned off, it could eventually wear the face of the sensor away.
I think these are magnetic pickups. All they do is supply electrical "pulses" to the ABS computer as the wheel turns. The faster the wheel turns, the faster the rate of pulses. There is one for each wheel. When one or more wheel suddenly locks up, the pulses stop, and this is how the ABS computer knows to release the hydraulic pressure to the affected caliper momentarily to get the wheel turning again. Some ABS systems can modulate the pressure up to 7 times per second, per wheel. This is why you get the hammering effect when you got the binder pedal down hard.
The computer is making sure the wheels don't lock, therefore, you don't loose traction.
This is why a good accumulator is so important. It stores energy in the form of pressurized brake fluid. When the ABS computer releases brake pressure on a wheel and has determined that it's speed has increased, it re-applies the brake pressure, and the accumulator is the device that supplies high pressure brake fluid on demand.
The pump is not sized big enough to modulate all four wheels.
It's kind of like that jet pump and water tank in your basement....only a lot higher pressure and brake fluid tastes like poo.
 
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