ABS and TC lights

[guruerror]

Originally Posted by HUMTECH

And 4 wheel drive buttons still don't work?

Nope. When I press 4HI LOCK or 4LO they just blink for a while and the truck stays in 4WD.

Originally Posted by jsbihn

So with the Actron you were able to clear all the code except the U1000 communication code?
So did the lights stay on the dash?
Have you experienced any difference in the way the truck runs?
Do you still have the issue with the transmission not being able to switch out of the selected 4WD?

Also, why do you think a tech2 will perform any different then what your Actron has performed?

The Actron cleared everything that it detected, including the U1000. As soon as I fired the truck back up the ABS, TC, and Parking Brake light all came back on and U1000 reappeared as a 'current' code.

There's nothing different in the way it drives...I just have no ABS nor can I switch 4WD modes. Other than that it runs normal. No 'reduced power', no 'service 4WD' indicators...nothing but these stinking lights.

I believe the Tech2 is better equipped to troubleshoot the problem based on the live data readings from the bus...or lack there of from a specific module.

I wasn't in the mood to fiddle with it today...instead I chose to honor MLK by planting my ass on the couch and playing XBOX.

[jsbihn]

Originally Posted by guruerror

I wasn't in the mood to fiddle with it today...instead I chose to honor MLK by planting my ass on the couch and playing XBOX.

Then you, my friend, have done what almost every person in America that MLK "fought for their rights" have done to "honor" him
So lets crack another 40 in his behalf

[BUNNY15]

Originally Posted by guruerror

Nope. When I press 4HI LOCK or 4LO they just blink for a while and the truck stays in 4WD.


The Actron cleared everything that it detected, including the U1000. As soon as I fired the truck back up the ABS, TC, and Parking Brake light all came back on and U1000 reappeared as a 'current' code.

There's nothing different in the way it drives...I just have no ABS nor can I switch 4WD modes. Other than that it runs normal. No 'reduced power', no 'service 4WD' indicators...nothing but these stinking lights.

I believe the Tech2 is better equipped to troubleshoot the problem based on the live data readings from the bus...or lack there of from a specific module.

I wasn't in the mood to fiddle with it today...instead I chose to honor MLK by planting my ass on the couch and playing XBOX.

Any luck figuring this out? I have the same TC and ABS lights on and no switching into 4H or 4L.

[Ken Bowers]

My orange 2003 Hummer also likes to give me TC and ABS alarms on cold mornings; especially on Monday after the orange H2 has sat without running over the weekend. The alarms clear after the ignition switch is turned off.

I believe it is due to low battery voltage.

[guruerror]

Originally Posted by BUNNY15

Any luck figuring this out? I have the same TC and ABS lights on and no switching into 4H or 4L.

BUNNY...no, I haven't figured it out yet. I personally think I've damaged the ABS module or some other control module from repeatedly running it through deep water. I still get the TC, ABS, and Parking Brake lights...typically all three, sometimes only two of the three; but eventually they all three light up again.

I've been rolling with it as is for a while since it drives fine...and because I have no off-road trips planned until Sept.

I got some additional input on a 'possible' culprit today though. I had to have the evap line for the AC replaced and asked the tech (local Midas shop) to give me his thoughts on my squeaky rear brakes. He said that my rear bearings have some play, which is causing the brakes to make noise at low speeds when applying slight pressure to the pedal. He went on to say that this 'play' could also be throwing my wheel speed sensors out of whack and hence causing the ABS, TC, etc. lights to come on. I passed on the repair for now, but thought it was worth a mention. I'm not sold on the idea that my WSS are causing my particular problem, especially since I also can't shift my transfer case; but what do I know...I'm not a trained mechanic, I'm just working off of layman's logic. EDIT: Actually I take that back...I just re-read some of HUMTECH's comments and he mentioned that I should check the "transfer case speed sensor wiring and connectors"...hmmm...maybe the Midas tech was on to something.

I scored a Tech2 scan tool a while back and plan on probing around in the truck this weekend or next to see what I can turn up on my own to help me diagnose. There's a little bit of a learning curve with the Tech2 'cause there's just so many options it's a bit overwhelming and not something that you can just 'jump right into'...unless you're merely scanning for DTCs.

I know I haven't been on in a while, but will make an effort to post back more results after I get the Tech2 on the truck.

[HUMTECH]

These DTCs set when the control module does not receive a message that it was expecting from another control module, and does not know which control module did not send that message.

 1. If the DTC U1000 or U1255 is set in history with other DTCs set current or history, diagnose the other DTCs first.
 2. If the DTC U1000 or U1255 set current, this usually indicates a module that is currently not communicating or a configuration issue.
For example, if the control module is configured for an option (ie: Onstar, Keyless Entry, Memory Mirrors, etc.) that the vehicle does not have, it may expect to receive a message regarding this missing feature. This would usually occur due to the control module being recently replaced and incorrectly setup.

 3. When the DTC U1000 or U1255 is current, the module that is not communicating may not even be listed on the Tech 2 on the Diagnostic Circuit Check/Class 2 Message Monitor list.
 4. If the DTC U1000 or U1255 has set in history without other DTCs, replacing the control module setting the DTC is most likely NOT the solution. The module that has set the code is looking for an input from another module that is not communicating. Since the module did not receive an input that it is expecting to see, it sets a U1000 or U1255 which indicates there was a loss of communications. Look at the customer?s complaint (ie: intermittent, erratic tachometer operation); this will probably be a better indication of the control module that is the source of the concern.

[HUMTECH]

If you don't have any ABS speed sensor codes set in the EBCM its not gonna be a speed sensor problem. If the Midas guy was pulling in and out on the tire and it moves slightly that is normal with a c-clip type semi floating axle

[guruerror]

This'll be the weekend to tackle more troubleshooting...

One thing I noticed that probably does rule out WSS...I discovered that Cruise Control is still operational; and from what I've read on other GM forums CC (obviously, I guess) relies on WSS.

[guruerror]

Okay...I hooked up the Tech 2 and did some rooting around...

Under Powertrain | DTC | DTC Info I pulled U1301 Class 2 High Voltage.
Under Powertrain | ATC DTC Info I pulled U1000 Class 2 Malfunction

Under Body I get two messages before entering the options menu (I'm gonna open another thread on this because I physically removed both of these and just need to get them out of the BCM programming):
OnStar/VCIM not responding
Digital radio receiver not responding

Under Body | SIR I pulled U1000 Class 2 Malfunction, B0100 Air Bag Sensor 1, and B0103 Air Bag Sensor 2 (the air bag codes are probably due to the fact that I just had front end work done due to trail damage...I think they busted both my front sensors.)

When I go under Chassis and try to go under ABS I get a message stating "ABS braking not available when the ABS/TCS lamps are illuminated." Then under ABS it reports "Loss of communication with vehicle"

[HUMTECH]

so you have a U1000 set in the air bag module(SDM)? I would check condition of module as it is located under drivers seat. If you have had water in the truck it will saturate the underlay and corrode the module pretty bad. If its messing up it can pull the class 2 data line down and cause problems on the network

[guruerror]

Ug...that's the unit that's under the carpet, right? Well...I never had water in the truck...but if it's not a monumental pain in the ass I guess I'll try an take a look at it.

[BUNNY15]

Originally Posted by guruerror

BUNNY...no, I haven't figured it out yet. I personally think I've damaged the ABS module or some other control module from repeatedly running it through deep water. I still get the TC, ABS, and Parking Brake lights...typically all three, sometimes only two of the three; but eventually they all three light up again.

I've been rolling with it as is for a while since it drives fine...and because I have no off-road trips planned until Sept.

I got some additional input on a 'possible' culprit today though. I had to have the evap line for the AC replaced and asked the tech (local Midas shop) to give me his thoughts on my squeaky rear brakes. He said that my rear bearings have some play, which is causing the brakes to make noise at low speeds when applying slight pressure to the pedal. He went on to say that this 'play' could also be throwing my wheel speed sensors out of whack and hence causing the ABS, TC, etc. lights to come on. I passed on the repair for now, but thought it was worth a mention. I'm not sold on the idea that my WSS are causing my particular problem, especially since I also can't shift my transfer case; but what do I know...I'm not a trained mechanic, I'm just working off of layman's logic. EDIT: Actually I take that back...I just re-read some of HUMTECH's comments and he mentioned that I should check the "transfer case speed sensor wiring and connectors"...hmmm...maybe the Midas tech was on to something.

I scored a Tech2 scan tool a while back and plan on probing around in the truck this weekend or next to see what I can turn up on my own to help me diagnose. There's a little bit of a learning curve with the Tech2 'cause there's just so many options it's a bit overwhelming and not something that you can just 'jump right into'...unless you're merely scanning for DTCs.

I know I haven't been on in a while, but will make an effort to post back more results after I get the Tech2 on the truck.

My lights are STILL on and on some starts they are off until I drive a few miles, then they come back on and stay on. Idk the problem, but I haven't had a need for 4WD in a while, so it's not the biggest problem to have right now. Need to get it fixed before November though.

[guruerror]

A little update on this...

I got it in my head this past weekend to double-check all the fuses in the truck...ALL of them...even ones that have nothing to do with ABS or TC. So, I disconnected the positive from the battery and pulled and tested every single fuse from both blocks (under the hood and driver's side dash).

Oddly enough...since I've slapped it all back together I no longer have the TC light. I've still got ABS and BRAKE lit...but NO TC; and it's been about 5 days now. I still can't shift the transfer case...but I thought it was interesting that the TC light went away.

They'll be more updates to come very soon since I finally dropped the truck off at the shop last night to have them diagnose. I'll keep you posted on the outcome.

[guruerror]

Got the truck back from the dealer yesterday...their diagnosis regarding the ABS/TC lights is that I need a new ABS module AND wiring harness ($1,495 installed).

They went on to say that the ABS/TC issue is NOT related to my inability to shift my transfer case. They said that I need a new encoder motor ($641 installed).

They indicated that both the ABS module and the encoder motor suffer from water damage. While I agree that they have both seen a lot of water I find it hard to believe that they both failed from water damage simultaneously. These components seem to have a fairly water tight construction and the connectors all have water tight grommets and were VERY clean and debris free when I inspected them.

I'm sort of feel like they're using the 'shotgun effect' to fix this problem...basically, replace a bunch of parts to fix one problem instead of figuring out which part is the actual culprit.

I've asked them to send me over a detailed estimate outlining the part numbers for the items that they would recommend replacing...at the very least that will give me a little more to go on. I'll post back once I have that in hand.

[BUNNY15]

**UPDATE** After 2 months of being at the shop, I finally picked up my boy 2TUF4U.

So to recap, he was leaking fluid in the driveway pretty heavy. I thought it was tranny fluid, but it turned out to be a cracked T-case. Replaced the entire T-case with a rebuilt one, and also the "extension housing" (?) which was also leaking. No more leak, but T-case switch still blinks and won't shift to 4H or 4L. Rebuilt T-case came with a new encoder motor. The mechanic wasn't sure if it was working, so he ordered another new encoder motor. Still wouldn't engage electronically; however the case could be engaged manually.

Next, purchased a new GM T-case switch from the dealer, installed it and lights still just blink. ABS and TC lights are still on, but remember, the last time they went off, T-case shifted as directed. I am unsure if the lights are related to the switch issue, but it sure seems like it. The dealer said on my 03 model, there is a control module under the dash. Rarely does it go out, but that may be the culprit of the switch failing.

Still uncertain if the two problems are related, but for an$120 diagnostic fee, I guess since it's drive-able now, I will take to the dealer soon.

$1959 dollars later, what's another $120 to know what's wrong exactly.

I'll update once I know something. Hell, maybe I'll pony over another $400 bucks and have the front seat warmers fixed before these TX winters get here