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2005 gmc envoy_sle
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Discussion Starter #1
A couple months ago I had someone in traffic tell me I had no brake lights, so I get home and check and both left and right brake lights are not working but the upper middle one is working fine. I get the correct new bulbs from autozone and swap out the old with the new ones, I start the truck to test it out and to my surprise the ABS and Parking Brake lights are on. It's been like this a couple months now and and I have tried to see if the ABS is really not working and they definitely are not, tried slamming the brakes on a wet road and full lock up. I read a few post about a bad ground under the drivers seat on the frame, I took mine off cleaned it up and put it back on with no luck. I've unplugged battery a few times and the light just remain on. I really can't figure out what happened, all I did was change the bulbs. I have yet to get the code read as my scanner doesn't read ABS codes, so I guess that's my next step. But, can anyone point me in a direction here? I'm kind of at a loss at this point. Truck is a 2005 Envoy SLE.
 

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2002 chevy trailblazer_ls
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I have yet to get the code read as my scanner doesn't read ABS codes, so I guess that's my next step.
Do you have access to a GM Tech II or high end scanners? Snap On, Mac, Matco?...Possibly check with local AutoZone about their loaner code readers...I'm sure once you get those codes, you'll know what direction to go...
 

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2005 gmc envoy_sle
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Discussion Starter #4
You could also look into the ignition switch, do a search on the form here for the how to.
Ok just a question but how could the ignition switch be related to the brakes? I looked at a post showing how to replace it which seems very easy, just not sure yet as to how that could be the problem.
 

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2003 chevy trailblazer_lt_ext
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Have you had a chance to put a scanner on yet to read codes? I wouldn't spend much time on chasing ghosts until I could narrow it down a little more. It could be a number of things but until you diagnose and identify what codes your spinning your wheels.
 

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2005 gmc envoy_sle
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Discussion Starter #6
Asked the guy at autozone here today and for whatever reason they didn't have a reader handy that checks ABS codes.
 

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Discussion Starter #7 (Edited)
Ok I finally got the ABS code read and it showed code U1000 Class 2 Data Link Malfunction. It's still a mystery to me to how this happened. The problem started when I replaced the left and right brake light bulbs. Any help here would be great as I have no idea where to begin.

Thing I've done recently to the vehicle:

Changed rear brake light bulbs

Cleaned throttle body (a check engine light would come on randomly relating to dirty throttle body, can't remember exact code but hasn't come back since cleaning throttle body)

Changed secondary air injection pump and check valve (was making crazy whining noise on cold starts, changing it solved this)

Changed rear brake pads

Checked brake fluid reservoir (Full)

Reseated ground wire directly under drivers seat area on frame (which was an attempted fix to the ABS/Parking Brake light being) The original washer that was on the bolt holding the wire to the frame had broken off while trying to clean it so I cut it back slightly so clean wire was actually touching the frame. But made no difference with the ABS/Parking brake light being on.

That is basically it. The ABS is definitely not working, and there is no check engine lights on other than the ABS/Parking Brake light. The truck runs perfectly otherwise, no other issues other than it need ball joints soon. I'd really like to fix this soon as I had a close call on the highway, full lock up and screeching forward, not nice. Again any help would be great. Thank you.
 

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2002 chevy trailblazer_ls
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Do a search for EBCM...Sometimes repairing the ground that you already worked on will take care of the problem, obviously not in your case...My buddy's '05 Silverado has this condition, our next step is to have the EBCM repaired...I found a service online...Good luck...
 

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2002 chevy trailblazer_lt
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Same Problem

Mine were on before I changed both front wheel hubs & both rear emergency brake shoes. I had to take a wire wheel on a grinder to the inside of both of my rear rotors so they would fit over the e.brake shoes. After that work was done, still on. Tried disconnecting the neg. side of battery, no luck.

I had the ASE Master Mechanic at my work scan my 2002 TB, just like at a dealership & it said there was a problem in the brake system not getting power. He said check the brake fuse and relay. Will update after my research.
 

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2005 gmc envoy_sle
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Discussion Starter #10
Mine were on before I changed both front wheel hubs & both rear emergency brake shoes. I had to take a wire wheel on a grinder to the inside of both of my rear rotors so they would fit over the e.brake shoes. After that work was done, still on. Tried disconnecting the neg. side of battery, no luck.

I had the ASE Master Mechanic at my work scan my 2002 TB, just like at a dealership & it said there was a problem in the brake system not getting power. He said check the brake fuse and relay. Will update after my research.
Hey thanks for the response, I don't know what to do at this point. I am not familiar with how to check if certain things are getting power or not like fuses and relays. Although I'm pretty sure I checked a few fuses that are involved with the ABS and they were all good. My next idea would be to change the ignition switch or the EBCM. The ignition switch being the cheaper and easier to change considering the EBCM needs to be dealer programmed, I might go that route until I discover something else.
 

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Discussion Starter #11
Ok so today I changed the ignition switch with a brand new one and both ABS and Parking Brake lights are still on. I followed a video tutorial that was very detailed, the switch is definitely installed correctly. Put the negative wire back to the battery, start the truck and both lights are still on.

Can anyone recommend what is best to try next? EBCM? Or should I check something else first, fuses? Relay? If so which ones? Is there anything I can check to see if it's getting power?.

Again both ABS and Parking Brake lights stayed illuminated constantly, they don't flash or chime they're just instantly on as soon as I start the truck and then stay on the entire time it's running. No other associated symptoms that I'm aware of, AC/Heat all work, no other warning lights of any kind. Any help would be appreciated.
 

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Discussion Starter #12
Been looking at a few different threads about this problem of mine and I am running out of options. I've come across THIS THREAD that I am having a hard time following. The second part describing the diagnosis if I am reading it correctly has me leaning towards the EBCM malfunctioning, for example it says "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."

I am having no other issues with tachometer or heat/ac blower or 4x4 or any other warning lights. The only problem I am having is with the ABS. So according to that thread does that mean since I am experiencing only one problem which is with the ABS could it be only that module that is not working?

Also if possible could someone help me understand the pic I posted of my ABS code being read? It looks to me that it is the only DTC as it states 1/1 but I'm having a hard time understanding if the code is set as history or current. Both seem highlighted on the screen.

I've already changed the ignition switch with a new one so I'm assuming the problem wasn't there. Although I didn't check for power at the locations it mentions in that post I linked.

Also if possible could someone list all the fuses involved with the ABS? Or any fuses or relays that could be involved in that U1000 code?
 

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Discussion Starter #13
I have been looking at a few other posts about wheel speed sensors or ABS sensors being a problem causing the ABS light to come on. Are wheel speed sensors and ABS sensor the same thing and also could a faulty one been my problem here? Thanks for any help, I'm really wanting to fix this already.
 

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2004 gmc envoy_slt
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First of all, you need to have the truck scanned by a high-end scan tool for the ABS problem. I think the U1000 is just a general data bus error and probably not related to the ABS.
The thing you can do right away is to check the following fuses; #33 in underhood fuse box and #51 in rear fuse box. Check them with an ohmmeter if you have access to one.
The front wheel speed sensors are used by the ABS system to determine wheel slip and they can cause the ABS to fault if they are not working correctly. The only way to check their function is with a high-end scan tool.
I can't understand how changing brake bulbs can cause ABS system problems. If the fuses check out OK, I think you will need to seek professional help. Throwing parts at a problem is expensive.
 

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Discussion Starter #15
Hey man thank you for your response. Yeah, I **** you not it happened just like that. I changed the bulbs and went to start the truck and both ABS and Parking Brake lights were on and have been on ever since. Literally nothing else was done to the truck prior to that. I am unaware of how long they were out for. As I am recalling the events in my head with the brake light issue, I believe I took out the turn signal bulbs which are the same exact bulb as the brake light bulb and put inserted them into where the brake light bulbs go and tried to see if it was infact bad bulbs and tried hitting the brakes and they both worked so I knew the bulbs that were in the brake light bulb slots were both bad. I then drove to autozone with a different car came back, put new bulbs in and started truck and both warning light were illuminated.

I will definitely check those fuses you mention asap. As far as the scan tool, can you be more specific on what you mean by high end scan tool? The one the guy at Advanced Auto used he said would read ABS codes, I believe he said it was around $200 to buy it. The one I have is just a normal ODB2 scanner which does not read ABS codes. In that pic I uploaded earlier in this thread you can see the scanner the guy used.
 

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I'm talking like a GM Tech II or a Snap-on scan tool, something like a well equipped shop would have. I think you need more than fault codes read, these tools can read actual data, like form the wheel speed sensors.
 

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Discussion Starter #19 (Edited)
Sorry I haven't updated this post. After all I did it ended up being the fuse that I thought I checked. Some how the fuse was missing all together and I have no memory of taking it out at all. Very strange! I cannot remember what number fuse but it was one involving the ABS I believe under the back seat. Putting a new one it was an instant fix. Good luck!
 
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