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[Brynjaminjones]

Does anybody know what kind of computer-thing I'd need to pull ABS data from my XJ?


It keeps activating at low speed and it's getting quite annoying. I'd like to figure out which wheel it is before throwing more money at it! I'm hoping there's some way of plugging something into the OBD port and watching the readings, but my understanding is that not everything can read the ABS system.

[gazjeep]

From memory, isn't the biggest XJ ABS issue crap / rusty tine rings causing the system not to be able to count the teeth / grooves properly ?

Get the wheels off & give them a good look over & clean before spending too much mate

[Brynjaminjones]

From memory, isn't the biggest XJ ABS issue crap / rusty tine rings causing the system not to be able to count the teeth / grooves properly ?

Get the wheels off & give them a good look over & clean before spending too much mate

That's the trouble - this problem initially started because one of the rings had rusted out and broken. I replaced the ring but slightly damaged a couple of teeth in the process, so I still had intermittent issues with it kicking in when it shouldn't.
I put up with that for a year and I've finally put another ring on it, but the problem is still there so I have no idea what's causing it now. 


All four rings look to be in good condition, so I want to see what's actually happening before I faff about with them any more!

[JamesH]

It could simply be a sensor gone. Finding out which one can be tricky. I’ve just paid a garage to do it for me (Bubba would be shaking his head and also cursing electrickery).

[Dutch]

(Bubba would be shaking his head and also cursing electrickery).

Now you mention Kev.  Since quite a few of the old stalwarts decided not be active anymore ....  anybody know how he is doing & the family ?

[JamesH]

(Bubba would be shaking his head and also cursing electrickery).

Now you mention Kev.  Since quite a few of the old stalwarts decided not be active anymore ....  anybody know how he is doing & the family ?

I think the modern phrase is “it’s complicated”! 

[Dave69]

the system isnt that technical to pull or see sensor data unfortunately.

a case of pulling the sensor and cleaning the crud and metal stuck to it and putting it back in place. the sensors are simple hall effect units which record pulse from the tone wheel in the axle.

you could always pull the ABS fuse and drive without it, wont affect the safety of the vehicle unless you brake that late and hard and that the reason for the issue?

[Jonny Jeep]

Sensors can be checked with a multimeter. Resistance should be between 900-1300 ohms.
Front sensor air gap to tone ring is non adjustable and should be between 14-59 thou of an inch.
Rear is adjustable and should be 36-50 thou.

I know from jeepforum that there have been a few issues with TJ ABS units. I can't remember if they were coming in without locking up or not coming in at all. The issue in those was corrosion inside the ABS valve block, and the fix was to source a used replacement.

[Brynjaminjones]

Thanks all for the advice. It's a shame the data can't be read real-time - I had hoped that maybe the dealer DRBIII or similar could do it.

Dave, I have thought of pulling the fuse and running like that. Our ZJ hasn't had the ABS working since we bought it in 2015 and it's never been a problem. If anything, the ABS in my XJ has nearly caused more accidents than it's prevented. I remember once sliding all the way down a field, nearly hitting the wall at the bottom when the ABS wouldn't let the wheels skid!

I'm not braking late, so that's not the cause of this issue. It's actually trying to creep to a gentle stop without a jolt that triggers the ABS most frequently.

The air gap on all the sensors seems good. I recently adjusted the rear ones after having the axle shafts out. The front ones seem fine too. I've cleaned all the sensors as part of this too.

I think the next thing is to measure the resistance on the sensors. I'll try that and see if anything seems odd!