ABS sensor question...

[Robman]

Can screwed up front abs sensors make the 4 wheel drive stay on?

2000 4.0L OHV Sport 5speed manual transmission with automatic 4x4.

 

[XLTrunner]

I had a passenger side ABS sensor go bad last Fall (light on dash stayed on) and it had no effect on the 4WD.

 

[koda2000]

Does your 4WD switch say AUTO on it? If it does a bad ABS sensor might effect 4WD engagement.

 

[Robman]

Well, I had a slight wobble in the passenger side front, I thought it could have been the rotor though I couldn't feel it in the brake pedal...so other than the rotor I thought it could be the tire.

I took the front tires off and checked out the rotors, then I got the bright idea to try and take the abs sensors out of the wheel bearings and clean them off as the abs light is on. Well that was a stupid idea as I slightly damaged one of them and then full on broke the passenger side sensor. I moved the bearing as much as I could with it still on and it seemed rough so I swapped it out with a used one I had lying around, besides I had broke the sensor on that side.
I had spare rotors I was going to put on that are in like new condition that I pulled off an explorer at the scrap yard but the damn things have a larger diameter than the rotors on my truck. Did some explorers get bigger front rotors?

Now there's a slight hum up there even after switching the tires front to back.

The hum sounds weird though almost like 4x4 is still engaged but it's probably the used wheel bearing I put in. I haven't looked into the 4x4 part too thoroughly, like leaving it in auto and going in some mud to see if the 4x4 clunks on.

Meh, time for a few new wheel bearings I guess and eventually new tires.

*edit - Yeah Koda, the Auto/4hi/4low selector knob.

I figured if the front sensors were buggered, the truck would think the front and back wheels weren't going at the same speed and put the 4wd on... is this correct thinking?

 

[koda2000]

"*edit - Yeah Koda, the Auto/4hi/4low selector knob.

I figured if the front sensors were buggered, the truck would think the front and back wheels weren't going at the same speed and put the 4wd on... is this correct thinking?"

That's what I'm thinking may be happening. The truck must use the ABS sensor info to turn the 4WD on in AUTO mode. Are you familiar with the brown wire mod? By cutting or adding a switch to the brown wire you can effectively turn off the AUTO feature.

 

[XLTrunner]

It's been my understanding that the two Halls Effect sensors on the transfer case are what monitor the differences in axle rotation front to back and provide information for the proper distribution of power via the transfer case. I don't think the front ABS sensors have anything to do with it.

 

[Robman]

It's been my understanding that the two Halls Effect sensors on the transfer case are what monitor the differences in axle rotation front to back and provide information for the proper distribution of power via the transfer case. I don't think the front ABS sensors have anything to do with it.

That would make sense... anybody know 100% for certain?


@Koda2000, as for the brown wire mod, I've read about it lots of times, I think the wire is just behind the stereo right? Anyway I've never performed it... as good as 2wd Low burnouts sound, lol.

 

[imp]

@Robman
"Can screwed up front abs sensors make the 4 wheel drive stay on?

"anybody know 100% for certain?"

"I figured if the front sensors were buggered, the truck would think the front and back wheels weren't going at the same speed and put the 4wd on... is this correct thinking? "

"It's been my understanding that the two Halls Effect sensors on the transfer case are what monitor the differences in axle rotation front to back and provide information for the proper distribution of power via the transfer case. I don't think the front ABS sensors have anything to do with it."

1) Yes, of course. ABS Module continuously monitors wheel speeds, even when (especially when) brakes are not applied. A difference in wheel speeds beyond the programmed tolerance limit turns ON the front-drive clutch.

2) Yes. Been there, had it. Fought with it a long time. Solved it, but still not satisfied.

3) Yes.

4) Shaft speed sensors in the Transfer Case do not reflect the appropriate information needed to activate 4X4 AUTO. IMO, 4X4 AUTO is a PITA. Poor way to achieve a vehicle's capability of negotiating snow or similar 4X4 needed driving conditions. Build the vehicle to accomodate the inabilities of the moronic driver..,.......imp

 

[Robman]

Thankyou IMP! ... Well, now I really fear that 4wd is stuck on.

The SOHC and OHV under the hood fuse box is different isn't it?
This part here is kind of needy, but does anyone have a labeled picture with the proper layout? (4.0L OHV)

I can just pull the fuse for the 4wd under the hood to disable the doodad that engages the front driveshaft right?

I think I've found the proper diagram - going to pull the fuse and give it a try.
*edit - Ok, pulled that larger fuse under the hood for 4wd and all it did was make 4low not work, during the test drive the noise was still there.

Been looking for a fuse diagram for the inside fuse panel, I don't really see anything about the 4x4 in there.

Might just hope it's just the wheel bearing making the noise and get some new ones asap.

 

[koda2000]

It's been my understanding that the two Halls Effect sensors on the transfer case are what monitor the differences in axle rotation front to back and provide information for the proper distribution of power via the transfer case. I don't think the front ABS sensors have anything to do with it.

You may be correct, but as this started with the OP breaking an ABS sensor, it makes be wonder if they don't play a part AUTO function. I'm not a 4WD guy, but this seems logical to me.

 

[Robman]

*update:

I kept the same abs sensor and simply swapped out that wheel's bearing and the noise is gone, everything is back to normal.
The bearing I had put in before was pooched, since then I had even been in some goop/snow and the 4x4 worked fine.