ABS: help needed

[buzz_mn_58]

Need help with abs brakes.

Truck is front and rear abs, 2000 4x4.

Had abs scaned. They said only abs code was the rear. I unpluged rear sencer and sprayed conectors with elect. cleaner. Didnt help. Bought new sencer and installed. Didnt help.

Checked ohms on sencers Old rear..........1.83
new rear.........1.75
right front.........0.42
left front...........0.42

This has been a on and off proplem for awhile now, but now it wont reset and work. Front hubs seem to be tight, no play in the bearings. When abs light out, and steping on the brakes at low speed 10mph, abs pulses when wheels not slipping then light comes on. Also light will come on at faster speeds with out touching the brakes.

Please help trouble shoot this problem please. Thanks Buzz

 

[adsm08]

Your ABS is broken because you can't spell. Go back to 3rd grade, learn to spell "sensor" and it will be fixed.

Your wheel speed sensors can't be tested by checking resistance, they don't work that way. They generate AC voltage as the wheel spins.


Go get it on a scanner and find out which sensor is giving and erratic signal. It sounds like you have a broken or damaged tone ring. If the code was for the rear it may be the tone ring that is bolted between the ring gear and the carrier inside the diff. Not a common failure, but it is possible.

 

[buzz_mn_58]

I did have it scaned they said the rear. If I remove the rear diff. cover, would I be able to see a damage to the tone ring? Or could old grease and maybe shavings give it a bad reading? Anything else I should be looking at? Thanks, Buzz

 

[Earl43P]

It most likely is not the rear sensor because the speedometer is still working.
ABS module takes in the VSS signal, converts it for use by the PCM and speedometer.
Cruise Control also uses that signal, if equipped.

I'm gonna guess bad front sensor.

Buzz, I've got the 2000 EVTM. If you want some schematics, send me a PM with your e-mail address. I also have an idea how to track down which front sensor it is, by reading milli-volts and spinning the tires.

 

[adsm08]

To find damage to the rear tone ring you'd have to remove the cover and carefully turn the rear around the whole way and inspect it closely.

It is probably a front sensor ring anyway.

 

[buzz_mn_58]

I pulled one of the front SENSORs out of the hub. Looked in the little hole and spun the wheel slowly. From what I could tell it looked clean. Some of the lows of the ring had grease in then some didnt. The end of the sensor had a little nice clean green grease on it.
I tried to remove the other side front sensor, but it was stuck in there more then the first side. I quit be for I damage it, or broke the little o ring.

I read some where that rust came build up under these sensors, and lift them up so that the gap gets to be to much. Is this possibly what could be happening to mine?

Earl I PM you.

Thanks, Buzz

 

[Earl43P]

When I rebuilt the front end of my 2000 4wd a couple years ago, I used duckbill pliers to firmly grasp and lightly twist and wiggle the front ABS sensors out. It's best to give them a good soaking spray. The only thing holding it in after you remove the one bolt, is o-ring pressure and crud.

I used those ABS sensor holes to pump fresh grease into the unit bearing, while rotating.

If there is rust built up under your sensor, that unit bearing is toast.

 

[buzz_mn_58]

So what is your idea on how to test the front sensors?

 

[Earl43P]

Disconnect the harness for each sensor under the bumper.
Connect a good analog meter to the two sensor wires.
Set the meter to read mV (millivolts).
Spin that wheel at various speeds, note how much the meter deflects at each speed.
Repeat for the other wheel.
The one that deflects smoothly and greater is the good one. You may have to try different ranges, if your meter has that option.

If you've got a good DVM that reads frequency, that might show a bigger difference.

It should be very obvious which one's pulse is weaker.
Coincidentally, that should be the side that it pulls away from (other front brake is grabbing properly, the bad side gets ABS pulses).

In other words, if the right front feels like it is grabbing and pulling in that direction, the left sensor is bad.

If you think rust scale has lifted the sensor away from the bearing, clean the face of the mount bore with some sandpaper and remount it and see if it helps.

 

[buzz_mn_58]

Wont have a chance to test sensors till after Thanksgiving.
My wife said the abs light went out yesterday, and now the abs is working normal, for now.
Must be a bad wire some where. Or do sensors work then dont work, then work again?

 

[Earl43P]

There are no moving parts in the sensor, so I'd think its wiring could be the problem.

First place to look is the front sensor disconnects, clean those up. Then go to the underhood 4WABS module and remove install its connector repeatedly to wipe the connections clean.

 

[buzz_mn_58]

I drove truck 90 miles today, with the light off. Then while doing some city driving, the abs started pulsing on dry pavement, just before coming to a stop. It did this for about 5 stops then the light came on.

Just wanted to give a update.

 

[buzz_mn_58]

UPDATE......... Its fixed

It was a bad wire to the rear sensor. It was rubbing on the brake line above the rear axle up by the frame. the copper wire was almost rubbed all the way though. The fix was easy solderd the wires together, coated them with die electic grease then used srink tube to seal it up. finished it up with black tape.

Thank you to all that helped me.

Special Thanks to Earl43p, for PM ing me the wiring schematices.

 

[tx3nc]

Congrats.

 

[Jacks2K4x4]

UPDATE......... Its fixed

It was a bad wire to the rear sensor. It was rubbing on the brake line above the rear axle up by the frame. the copper wire was almost rubbed all the way though. The fix was easy solderd the wires together, coated them with die electic grease then used srink tube to seal it up. finished it up with black tape.

Thank you to all that helped me.

Special Thanks to Earl43p, for PM ing me the wiring schematices.

Hello buzz_mn. Which side of the frame, driver or passenger side? I have the ABS light on and my truck is the same year. Just want to check to see if it's the same issue. Thanks.