ABS and TC lights

[guruerror]

This message is primarily for HUMMTECH but PMs seem to be down, so I'm posting here. Feel free to reply.

Went wheeling through some deep (2-3 feet pretty consistently), icy water and got TC, ABS, and Parking Brake lights on and off the whole time. It's been a month and I've still got the lights on. Not always all three...but always ABS and TC.

I just pulled the positive off the battery, checked the rear wheel speed sensor cables, pulled the sensors out, cleaned everything and put it back together and took it for a drive. I still have the lights.

Thoughts?

Thanks in advance.

[jsbihn]

Did you scan for codes?

[guruerror]

Sorry...forgot. No codes at all.

[jsbihn]

I am definitely not HT, and I know that you probably know more about these "rigs" than I do, but do you think that possibly its either a computer issue (ie. you got the BCM or something wet), or the sensor (ie. they are wet or damp or something.... even though I know you cleaned them and such) or that maybe the dash is malfunctioning?

Plus the fact that it is an intermittant problem....
Do you have anything that is not performing correctly to correlate with the light?

Again... not an expert but based off standard GM OBD I would think that if you have a light you should have a code... sometimes you even have codes with no lights (Ie. no CEL on my vette, but I have a couple of codes pop up on every start up because the O2 sensors are not a fan of my headers)

[HUMTECH]

What did you scan for codes with? If its a code reader it wont pick up chassis codes. Need a pretty good scan tool to get codes from ebcm. I would start there but you could look at transfer case speed sensor wiring and connectors for damage, water intrusion in connector at speed sensors. I bet there is codes set in ebcm with those lights on.

[guruerror]

I used my SuperChips Cortex programmer to look for codes. I'll check the transfer case tomorrow and maybe swing by the old Hummer dealer to have them scan it.

Thanks...I'll report back.

[guruerror]

I checked the cable going into the transfer case. There's no visible damage...it was mud crusted, but I disconnected it, cleaned it, applied some dielectric grease and reassembled. Took it for a drive...still got the lights.

I was feeling lazy so I took it to Advanced Auto to have them pull codes instead of the dealer. Here's what came up on their scan tool:

U1305
U1000
U1040
U1016
P1626
U1301

Most of these seem to deal with serial communication errors. I'm starting to think that I've damaged some part of the on-board computer system. I also noticed that the 4WD is out. I can no longer switch to 4HI or 4LO.

LOL...looks like I'll be off to the dealer before my next adventure.

[HUMTECH]

I will throw a guess out that you have lost communication with your electronic brake control module. Check abs fuses and inspect connector at abs module for damage or contamination.

[jsbihn]

I had a feeling there was a computer issue based on the fact that usually if there is an issue with that much involved in the Vette it has to be a bad sensor, wire, or module.

Did you have them clear the codes to see if they were active or history codes?
I always do that because active codes will mean a broken something. The codes will not clear. history codes will give u issues but if cleared and they never come back then it was probably a one time drop in voltage or something.

(ie. after I had the s/c installed on the Vette my car would constantly drop into "limp mode" for no reason. Sometimes if i floor it, other times if i dont. Sometime if i just drive it normal.... there seemed to be nothing to cause it. Since the installed was in a far away state I couldnt easily bring it to them, so 1500 dollars later my tech finds it is the crimp connector used for the TB. turns out these computers are so sensative that the slightest drop in voltage will through a code. After a quick clip clip and solder, the car has been strong ever since.
I assume the Hummer is the same way

HT, do you think the ebcm or the abs module is causing the issue with his inability to shift his 4wd?

[HUMTECH]

Not sure on that. If you can clear all codes and it still wont shift that's where I would be looking for a failure. History communication codes are the hardest thing to diagnose. As per GM diagnostics you should never even chase one. Any module on the data line can be causing the problem. Don't remember if I asked but do you have a remote starter installed? P1626 tells me you might have one as its a security code. If you do the security bypass module for the remote starter could be root cause and that's where I always start for these type of issues.

[HUMTECH]

if not remote start the reason I would suspect ebcm is that its under the truck and ucodes that are set would be typical of that module causing a communication issue. If the ebcm is causing a data line problem the only module downstream of it is the transfer case shift control module

[jsbihn]

OK maybe I am a little nieve on these rigs, but doesnt it sound a little "off" for Hummer to place a computer outside the truck in an area that could easily go under water?

(Especially since these things are designated to be a more extreme off road vehicle?)

[guruerror]

Yep...there's a remote starter on the truck. The previous owner installed it. I've looked at pulling it several times, but it seems to be wired in in such a way that it can't be easily removed. HT, you're probably correct about that causing the P code, and I'm not convinced that the P code is related to everything else that's going on. I also recently installed a 'new' factory head unit...I thought this might be involved in the P code, but the unit works fine and was programmed for my VIN.

jsbihn, I didn't have them clear the codes. I think I'll probably swing by Pepboys this morning and grab me a good scanner to keep on hand. I'll clear them myself and see what happens.

I've also gotta pull up the EPC and figure out where the ABS module is located. The ABS fuse (60 amp, front fuse box) is good.

[guruerror]

Checked the ETC fuse (15 amp front fuse box)...it was good.

I found the ECBM up under the frame, driver's side...there's no physical damage that I can see. I couldn't figure out how to get the connector loose from the module to see if it's be contaminated, and it's a bit cold to be hanging out under the truck today. I'll figure this out later.

Going to grab a scan tool now...

[jsbihn]

HT,
Will a ELM 327 be able to scan down enough?
It appears on my Vette, it doesnt pick up all the codes that the car's ECU will scan and clear, but I could be wrong.
So I was wondering if it acted the same on the H2

[guruerror]

I grabbed an Innova 3130c...it picked up the P1626 and U1301. I cleared the codes and fired it up...still got the lights. Shut it down, rescanned...no codes reported. The 3130 is suppose to report ABS codes/status on GM vehicles too, but the tool reports that ABS communication with this vehicle is not supported. Weird...I'll have to research that a bit on Innova's site.

I'll drive it for a while and see if anything changes. I'll probably look at the EBCM again tomorrow...supposed to be a tad warmer.

[HUMTECH]

Try this. Right behind the data link connector where you plug scanner in you will find a wire spliced into the data line(purple wire) cut the added wire in a way you can reconnect it later. Then attempt to clear codes and see what happens. If the remote start is causing a data line failure this will eliminate it.

[guruerror]

HT, I'll check this out tomorrow, although I really don't think the remote starter is the culprit. You seem to know your business...so I'll definitely follow your guidance and report back.

I returned the Innova scanner as I wasn't entirely happy with it. The 'tech' at Advanced Auto used an Actron when he scanned and he got more codes than I got with the Innova. So I swapped the Innova 3130c for an Actron CP9580. The 9580 pulls the same codes that Advanced got (those listed earlier in this thread - minus the P code...that hasn't returned).

I used the Actron to clear all codes across the board. After firing the truck back up I got the U1000 only. My gut tells me that I'm going to need the dealer to slap a Tech2 on it to really get a diagnosis.

[HUMTECH]

And 4 wheel drive buttons still don't work?

[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?

[guruerror]

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.

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]

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.

:giggling: 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 :giggling:

[BUNNY15]

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]

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]

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. :crying:

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:jump: