service brake system

[v7guy]

If I'm not mistaken the readings for the rear on the 2002s come from the transfer case. So the readings aren't filtered through any gearing. If there is any reading from the axle then I could see a comparison between the front ABS sensor readings and the rear axle not matching. That would cause an issue. I'm not as well versed in our platform as I should be.
It also could be a coincidence and be completely unrelated. I've had this situation bite me a few times over the years. I'd be most inclined to think there's a fairly worn wheel bearing giving an off reading from the three different sensors.

[fishsticks]

Found this on the Transfer Case Operations Thread
If the sensors speed on the front hubs don't match the sensor speed on the front output shaft on the tranfer case could this be causing my problem?

Front Propshaft Speed Sensor

The transfer case shift control module converts the pulsating AC voltage from the font transfer case speed sensor to front propshaft speed in RPM to be used for calculations, and to monitor the difference between the front and rear sensor speed. It is also used in the AUTO (Adapt) mode of operation to determine the amount of slip and the percent of torque to apply to the front axle. The front propshaft speed can be displayed with a scan tool.

Service 4WD Indicator Lamp

I believe you found your problem.

While others (including myself) have spent some time with differing front/rear ratios, many were 06+ or had a smaller gap between the ratios. The gap between 3.42 and 4.10 must be enough to make the PCM throw codes.

[94 eg]

Well I got the 4.10 front diff installed Tuesday night and I'm still having the same problem

[v7guy]

Did you remember to plug back in all the abs sensors?

[94 eg]

Yep all the sensors are plugged up

[Trail X]

So when the guy scanned your system, it didn't give him any brake related error codes? Was there any difference between left and right front wheel speed sensors? Did your friend check for the ABS codes? They are not stored where a normal engine scanner can read them. I believe you need a Tech II or dealer computer.

If all else fails, I would attempt to get the gear ratio variable changed in the computer - I'm sure pcm4less can do that, along with anyone with the right software.

[94 eg]

Yeah when he scanned it he just said the two front speed sensors were reading different than the rear. He didn't actually tell me what code it was. He said the rear was reading faster than the front. He was using one of the high dollar snap-on scanners, not sure which model.

[navigator]

in an earlier post you mentioned you changed tires to 33's. Are they approximately the same height/wear or could the front/rear be more worn than the others.

I would be surprised if even a new vs used tire would throw the sensors off enough to matter but it seems you have tried everything else.

[94 eg]

Yes I bought all the tires at the same time and they only have about 7k on them. I rotated them at 5k and they look to be wearing nice and even so I don't think thats the problem. I'm going to give PCMForLess a call and see if they can fix the issue or at least get the lights to quit coming on.

[v7guy]

Maybe a bad sensor at the transfer case?
It would be fairly unlikely that both front sensors would be bad and still syncing with each other.

[94 eg]

I got it scanned again today and the code is a C0238 Wheel Speed Mismatch
This is the only code besides a old P0130B for the o2 sensor and a P0128B for the Coolant Thermostat

[94 eg]

Ok so I went and made a video logging the sensors. You will notice that the rear sensor starts off reading faster than the front and once I slow down it gets in sync with the front two sensors.

http://www.youtube.com/watch?v=xlwmvshD8FI

[94 eg]

Just talked to PCMforless and the guy told me being the its a 02-05 I'm screwed as far as them being able to reprogram the speed signal.

[v7guy]

Have you ever swapped out the rear sensor? It's mighty peculiar that it starts off getting out of wack at higher speeds but then starts to read in sync with the front after a bit. It seems that its caused by the rear sensor reading wrong.
Does it ever start to read out of wack again after you drive for awhile or does it stay in sync after the initial screwy behavior?

[94 eg]

I didn't get a chance to drive it much when I had the scan tool. I will try to get it again this weekend so I can take a long drive and see it if acts up after the first time.