ABS Freakout

[TWITCH101]

So I was driving to pick up some friends on my way to the airstrip to go skydiving and had a little incident with what I'm pretty sure is the ABS.
I had been on the interstate cruising at about 85-90ish and took an exit to meet some buddies at a gas station to carpool another 50 miles. Well I pull into the station and we get loaded up and ready to go in less than 10 minutes. I got to leave and less than 2 miles down the road I had to stop at a red light. The car in front of me stopped very abruptly causing me to slam on my brakes. After slamming on the brakes I feel my brake pedal kind of push back and hear the ABS buzzing from what sounds like the other side of the firewall. THen the pedal went soft. I must say that not a single tire was locked up or else I would have felt it or heard it( I know what breaking the tires loose feels like).

So I'm wondering what my issue may be?
To make things clear I had an issue with my front left caliper a few months ago and it seized up and started dragging while I was driving and was even smoking. I replaced the line and bled the caliper and haven't had a problem since. But I will say that the rotor has significantly more wear than the other side. Haven't checked my pads yet. Might try that tomorrow if I can find some time.

Anyone have any ideas and or helpful info and insights?

 

[chauncey0337]

Does the truck pull to the left? That caliper may be going bad and I would replace it. Hopefully, it's not a problem with the abs system.

 

[DCT]

Hopefully it's just the caliper. Make you don't have a leak in the system somewhere. Unfortunately, the ABS pump issue is a known problem on our trucks. Mine has been replaced. They may be available to be rebuilt. I went with a new unit (damn expensive).

 

[TWITCH101]

how expensive? and to be honest the yukon pulls any direction on any day....some days it feels perfect and some days it feels like idk which way it will go when I hit the brakes.

---------- Post added at 09:14 AM ---------- Previous post was at 09:13 AM ----------

but I think its partly that the shop I had do my front end alignment didn't get it straight

 

[doylee4693]

Hopefully it's just the caliper. Make you don't have a leak in the system somewhere. Unfortunately, the ABS pump issue is a known problem on our trucks. Mine has been replaced. They may be available to be rebuilt. I went with a new unit (damn expensive).

Is it really because this is the first time hearing about a abs pump failing on these trucks.I have heard the module failing but thats is a cheap fix if you look on google and search for a repair service.If youre pump is done like dct says then thats 500 just for the part and I have no idea as far as labor goes.

 

[TWITCH101]

This doesn't sound good....

 

[delta579]

Sounds like that caliper is bad. Most OEM calipers have a plastic/nylon piston in them that get scarred in the caliper cylinder with use and will not retract back. Most aftermarket calipers have a stainless steel piston, check when you buy. Only buy the steel one. I would change out both calipers, if one is bad, then the other is close to it. Lube pins. This is cheapest thing to try first.

 

[TWITCH101]

Sounds like that caliper is bad. Most OEM calipers have a plastic/nylon piston in them that get scarred in the caliper cylinder with use and will not retract back. Most aftermarket calipers have a stainless steel piston, check when you buy. Only buy the steel one. I would change out both calipers, if one is bad, then the other is close to it. Lube pins. This is cheapest thing to try first.

What brand would you prefer? And about what should I expect it to cost?

 

[delta579]

It really doesn't matter which brand you use, they are about the same. Just take it out of the box and check the piston to make sure it's steel.
Cost ? I can't remember, but it's not bad. Check online AutoZone, Advance Auto, etc.

 

[DCT]

Is it really because this is the first time hearing about a abs pump failing on these trucks.I have heard the module failing but thats is a cheap fix if you look on google and search for a repair service.If youre pump is done like dct says then thats 500 just for the part and I have no idea as far as labor goes.

Check used car websites like Edmunds. Two known issues are brake pump and catalytic converters. Sorry, don't have a link available.

 

[TWITCH101]

catalytic converters???I guess you mean they get clogged? and what are symptoms of the abs pump going out?

 

[TWITCH101]

Went by autozone and they asked about a police edition caliper....I was like Wtf??? Is it a larger caliper or something? Anyone know if its any different or if it will bolt up?

 

[DCT]

catalytic converters???I guess you mean they get clogged? and what are symptoms of the abs pump going out?

Check Engine light.

 

[TWITCH101]

Ok so I was driving yesterday and hit a speed bump while applying the brakes and it caused my abs to go ape shit for about 2 seconds. I mean I could hear the pump going haywire and the brakes got very, very soft. Could this be my bearings are bad and this is causing my sensor to give a bad reading which is causing the abs to freak out?

 

[delta579]

Cheapest first. Check wheel sensor wires/connectors at both wheels. Replace wheel sensors. You should be able to hear/feel a bad wheel bearing when the truck is up and you spin the wheel.

 

[TWITCH101]

yea I had her up about 5k miles ago and couldn't feel anything but then again I dont think I know what a bad one feels like vs. a good one. but I need the resistance for the sensors so I can check them with a meter to know if they are good or not.

 

[delta579]

I don't know the resistance levels for the sensors. They are a magnetic pick-up sensor, no moving parts, similar to crank/camshaft sensor. It's highly improbable that both would go bad at the same time though. Check the resistance readings on both, it should be the same. If they are not, then go to your parts place, with your meter, and check the resistance on a new sensor. This should tell you if need a new sensor, and which one it is.
Wheel bearings ? Normally you will hear/feel a grinding/rubbing. Remove the tire and spin the rotor using the lugs. Metal transfers sound better than rubber. Use a stethoscope or length of fuel line(rubber or metal) against the bearing housing. Compare both right and left sides, there should be very little noise coming from the housing. Hope this helps.

 

[electro]

Measuring the wheel speed sensor using a mV scale while rotating the hub one revolution per second i believe is the correct way to check for a bad sensor.

The hub rotation will produce a mV. It should be 250mV or 350mV for a good one. I cant remember the correct number. I will check later.

This can prove difficult as a multi-meter with that scale is expensive.


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[Wake]

It could be as simple as a bad wheel speed sensor.

It wasn't on my Escalade but my previous SUV, a Trailblazer.

Stopping was fine until I was just about stopped and then the ABS would kick the pedal back at me. It's a weird feeling when your truck is fighting you on the brakes.

I hooked up a scan tool to the vehicle and saw the bad sensor on my right front wheel. It would intermittently drop out to zero MPH below 7-10 MPH, telling the ABS computer that a wheel had locked up and it would kick the ABS in.

Had it happen a second time about 3 years later (thanks crappy eBay wheel bearings) and ended up having to replace the bearing assembly as something was going on with the reluctor wheel inside that the sensor uses to determin speed.