Dreaded ABS Problem

Hi All,
New to forum. Just purchased 1998 XJ w/ 120K. Have set about fixing up issues and been using forum but have not needed to post since everything I've encountered was able to be addressed by searching old threads but....

ABS light is on and I am trying to diagnose w/ my limited skills. So far I have:
1) checked relay and all fuses (that I know of)
2) visually insp all sensors and lines (afraid to remove sensors since bolts are a little crusty)

3) checked box (module?) under rear seat for loose connections

4) jumped motor from battery and it runs

I want to bleed system and check sensors w/ meter but I don't know how. I pulled the bus off the modulator (think its modulator, attached to motor) and there are pins etc.
Anyone know the positions to probe for each sensor or is there a better way?

Thanks in advance

Bleeding won't help the ABS problem. Bad sensor probably, but you really need to pull the codes some way. You can probably test each sensor at where it plugs into each wiring harness. Have some one turn the wheel as you probe and see if you are getting a voltage that goes between 0 and some number. You can check resistance but I don't have a figure for that. You could check all 4 and see if anyone is significantly different.

I had the ABS light come on in my 2000 Limited. Found out the left rear sensor and tone ring were coated with grease/dirt. Bad axle seal seeping. Cleaned all the sensors and tone rings, adjusted the sensor so it was pretty close to the tone ring but not touching. You can try an auto parts store to get the codes read. I have bled the old way (pump-hold) and with a pressure bleeder. It takes more time and more fluid with ABS but works well.

IMHO disconnect it. relay in the PDC, fuse in the kicker panel, and all connectors under the rear seat. XJs don't really need ABS if you don't panic-lock them.

Kudos if ya can fix it though lol.

pokeyxj said:

I had the ABS light come on in my 2000 Limited. Found out the left rear sensor and tone ring were coated with grease/dirt. Bad axle seal seeping. Cleaned all the sensors and tone rings, adjusted the sensor so it was pretty close to the tone ring but not touching. You can try an auto parts store to get the codes read. I have bled the old way (pump-hold) and with a pressure bleeder. It takes more time and more fluid with ABS but works well.

Click to expand...

You aren't actually bleeding the ABS block that way unless you activate it while you are bleeding. I don't see it as necessary though as you are only going to get air into the ABS block if you activate abs with air in the lines.

Also, the sensors have an adjustable air gap of 0.036-0.05" rear and 0.014
to 0.059" front. New ones come with a piece of card board like used in a USPS Flat rate envelope glued to it. You just push that up against the tone ring to set the gap.

Well as far as bleeding, the left side rear brake line was replaced but the fluid does not look like it was changed out so thats in the might as well category.
Guess I'm going to have to trace back to each wheel sensor if I can and get a reading.
Pulling the plug on the ABS has crossed my mind! Especially when I'm laying under the dang thing, but its a 3rd car family truckster and the wife may have to drive so I'd like to fix it if I can.

Does anyone know, even after its fixed, does the code need to be cleared? Right now the pump motor does not turn on at start up. Assuming it is shut down until code is clear but not sure if thats how it works.

Talyn said:

You aren't actually bleeding the ABS block that way unless you activate it while you are bleeding. I don't see it as necessary though as you are only going to get air into the ABS block if you activate abs with air in the lines.

Also, the sensors have an adjustable air gap of 0.036-0.05" rear and 0.014
to 0.059" front. New ones come with a piece of card board like used in a USPS Flat rate envelope glued to it. You just push that up against the tone ring to set the gap.

Click to expand...

This is what I read as well, that key must be on while bleeding master cyl and block but since pump motor is not running unless jumped by battery how Emma gonna do dat?

jatoxico said:

Does anyone know, even after its fixed, does the code need to be cleared? Right now the pump motor does not turn on at start up. Assuming it is shut down until code is clear but not sure if thats how it works.

Click to expand...

The code will clear itself. I don't think the pump should be turning on at start though.

jatoxico said:

This is what I read as well, that key must be on while bleeding master cyl and block but since pump motor is not running unless jumped by battery how Emma gonna do dat?

Click to expand...

I see no reason to have the key on when bleeding the system. The FSM doesn't mention anything about that as well. To bleed the ABS by the book you need a DRB and activate the pump. Bleed as normal, activate pump, then bleed as normal again.

Talyn said:

The code will clear itself. I don't think the pump should be turning on at start though.

Hmm OK, I thought it was supposed to do a self diagnostic which meant the pump came on momentarily.

I see no reason to have the key on when bleeding the system. The FSM doesn't mention anything about that as well. To bleed the ABS by the book you need a DRB and activate the pump. Bleed as normal, activate pump, then bleed as normal again.

Click to expand...

The "key on" comes from the Haynes manual. Maybe leaves valves open?? Wish I had the FSM not too impressed with the Haynes, no detail and barely addresses a number of topics including the ABS.

Thanks for the other info, I'll check gaps. My tone rings are a bit rusty as well, not too bad but prob should take some emery paper to them.