# ABS light on



## mkwl (Jan 21, 2005)

Went out to my truck this AM- started the truck and the ABS light stayed on. Any thoughts? Just had the whole hub assembly changed with the ABS on that hub as well- anyone think it could be this? Anyone had this problem?


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## fordmstng66 (Dec 27, 2005)

I do not know if they fixed it, but the 2000 had problems with the sensor in the hub. Did your new hub assembly have the abs sensor in it? They so sell the hubs with and without the abs sensor i believe. If it did not, they probably just used the old one, and it could be dirty. That is just my .02 hope you fix the problem.


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## Spitz (Feb 28, 2008)

You're going to need to pull the code.. I would first just look at the connector for the side they put the hub on and make sure its fully seated first, and then see if the light goes out, if not, you're gunna have to get the code for further diagnosis.


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## mkwl (Jan 21, 2005)

Took it up there- plugged it in- no code thrown  They replaced the whole assembly- including he sensor- maybe a defective sensor in the hub? Not sure if it matters- but it's VERY humid and rainy out today- only did it this morning- not when it was dry out. Tried resetting the comp and re-plugging it in- no luck. :crying:


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## RichG53 (Sep 16, 2008)

Take it back you paid to have it fixed..


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## Scott13136 (Dec 25, 2008)

Mine comes on if i sping the tires to much, It clears itself eventually (02 2500hd)


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## Tango (Dec 2, 2008)

Scott13136;690162 said:


> Mine comes on if i sping the tires to much, It clears itself eventually (02 2500hd)


Mine does the same thing.


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## brad96z28 (Aug 21, 2005)

mkwl;689401 said:


> Took it up there- plugged it in- no code thrown  They replaced the whole assembly- including he sensor- maybe a defective sensor in the hub? Not sure if it matters- but it's VERY humid and rainy out today- only did it this morning- not when it was dry out. Tried resetting the comp and re-plugging it in- no luck. :crying:


If the light is on it has a code for sure.


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## mkwl (Jan 21, 2005)

This is the damndest thing- light came on again today- truck was sitting in the parking lot all day (not driven), hop in, and the amber ABS light is on  It was pouring rain all day, and very humid- same conditions as the light coming on before- maybe a bad ground somewhere?


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## naturalgreen (Dec 6, 2008)

sounds like maybe something grounding or arcing when wet


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## mkwl (Jan 21, 2005)

naturalgreen;839148 said:


> sounds like maybe something grounding or arcing when wet


That's what I'm thinking- problem is, all the grounds "look" okay- I'll have to dig deeper...


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## B&B (Nov 4, 2006)

mkwl;839196 said:


> That's what I'm thinking- problem is, all the grounds "look" okay


 They can "look" good all day long Matt..you have to physically remove them and clean them to know that they're truly good.

Don't forget the one under the driver door...there's three there and one of them is for the ABS unit.


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## mkwl (Jan 21, 2005)

B&B;839271 said:


> They can "look" good all day long Matt..you have to physically remove them and clean them to know that they're truly good.
> 
> Don't forget the one under the driver door...there's three there and one of them is for the ABS unit.


Makes sense- will look into this next time I'm home (the college police prohibit us for working on ANYTHING on vehicles on college property)- I assume then that it's possible for the moisture/rain to cause it to have a "bad" ground, but then it dries out and it's okay again?


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## Newdude (Dec 4, 2006)

Dumb question...is the abs sensor plugged in? Maybe the guy who fixed it forgot? Maybe the wires got pinched?


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## B&B (Nov 4, 2006)

Anythings possible Matt. A poor ground, a pulled wire causing an intermittent open connection at the wheel sensors etc. So you need to inspect and check them all.

Also, is it only the orange ABS light that illuminates or does the red brake light icon also light at the same time? Just checking, as there's TSB for that that has nothing to do with wiring, it's for a re-flash of the ABS unit. Plagued the '03 and 04 trucks for a few years after they were out.


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## Gregg1987 (Sep 30, 2009)

B&B;839689 said:


> Anythings possible Matt. A poor ground, a pulled wire causing an intermittent open connection at the wheel sensors etc. So you need to inspect and check them all.
> 
> Also, is it only the orange ABS light that illuminates or does the red brake light icon also light at the same time? Just checking, as there's TSB for that that has nothing to do with wiring, it's for a re-flash of the ABS unit. Plagued the '03 and 04 trucks for a few years after they were out.


What would cause both the ABS (orange) and Break light (red) to go on at the same time? Is that a huge issue?

i have an 01 3500 Duramax and they said that they were on previously but the issue was resolved before i saw the truck. (haven't seen the lights since i had it but they said that they were lit at one point) Seems fixed just curious what that would have been? Serious problem?


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## mkwl (Jan 21, 2005)

Over the summer it was coming on with both the red and amber lights. That issue "resolved itself." and I was good until the weekend.

This most recent time, just the amber ABS light was on- now it's off again.


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## mkwl (Jan 21, 2005)

When I had it scanned over the summer the code came up as "no communication with the EBCM" then it went away


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## B&B (Nov 4, 2006)

mkwl;842580 said:


> When I had it scanned over the summer the code came up as "no communication with the EBCM" then it went away


It needs the EBCM reflashed with the newest software version. That was a common issue with the '03-'04 models were when you started the truck the body control module didn't wait long enough before checking for the "a ok" power up from the EBCM. When it doesn't receive the ok signal in time they illuminate the brake icons and set the specific code you found. There's a TSB on it and it's an easy fix. Bulletin # is: 04-05-25-006A

You still have a wheel sensor issue too that isn't related to this so be sure to still check over your grounds and sensors like I mentioned before.


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## mkwl (Jan 21, 2005)

Thanks B&B- any idea how much the "flash" costs? It also seems to be very related to the moisture/rain (comes on when it's "wet" outside).


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## B&B (Nov 4, 2006)

Well it would depend on what your dealer charges per hour but I can tell you it pays .4 on the time so that's what they'll base the time charge on.


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## mkwl (Jan 21, 2005)

B&B;842715 said:


> Well it would depend on what your dealer charges per hour but I can tell you it pays .4 on the time so that's what they'll base the time charge on.


Okay- and you think that would be it, even though moisture seems to be a major contributing factor? Right now the lights are all off (knock on wood), so I think I'm just gonna leave it lie for a bit and see how it goes- if the ABS/Brake lights come on again, I'll probably go to get it flashed if you think that'll take care of it...the dealer told me I needed a whole new EBCM to the tune of $1,300


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## B&B (Nov 4, 2006)

Then I'd strongly advise going to a different dealer. That ones trying to sell you parts that I highly doubt you need.


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## mkwl (Jan 21, 2005)

Both lights are back on today... after a truck washing... I assume the truck will just not have ABS in this instance, right? Brakes feel normal to me- light will hopefully go off again when it dries out some.


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## B&B (Nov 4, 2006)

Any time you have an ABS "issue" that temporarily shuts down the system the brakes should still feel as they normally do.


Did it happen right after you started the truck? Did you have the updated reflash done?


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## 911tech (Dec 31, 2009)

The sesnor most likley needs to be cleaned. Pull the sensors out of the hub with the appropriate allen wrench and clean all the crap of of them. As you drive you get brake dust dirt salt ect, on them. When they get covered with grime they can't read the teeth on the cv shaft and assume that one wheel is going faster tripping the abs. Most likley its only one sesnor as is is tripping the light and not the actual abs system. should only take half hour to both sides. There also may be a kink in the sensors cable if the mechanic didn't route it right or use the factory wire holders. Had the same problem with mine, cleaned the sensors and never a problem after that.


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## B&B (Nov 4, 2006)

911tech;991052 said:


> The sesnor most likley needs to be cleaned. Pull the sensors out of the hub with the appropriate allen wrench and clean all the crap of of them. As you drive you get brake dust dirt salt ect, on them. When they get covered with grime they can't read the teeth on the cv shaft and assume that one wheel is going faster tripping the abs. Most likley its only one sesnor as is is tripping the light and not the actual abs system. should only take half hour to both sides. There also may be a kink in the sensors cable if the mechanic didn't route it right or use the factory wire holders. Had the same problem with mine, cleaned the sensors and never a problem after that.


The sensors don't read teeth (tone ring) on the CV on a Silverado, because there are no teeth on them, they're in the wheel bearing assembly. And if there's crud in there you've got bigger problems. The real issue there (sensor wise) is the corrosion buildup under the sensor on it's mounting flange. Plenty of reading on that specific subject here if you look around a little.


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## 2COR517 (Oct 23, 2008)

mkwl;990867 said:


> Both lights are back on today... after a truck washing... I assume the truck will just not have ABS in this instance, right? Brakes feel normal to me- light will hopefully go off again when it dries out some.


Matt - When you say both lights are on...
Do you mean the Amber ABS light and the Red Brake light?

The Red Brake light could indicate a serious problem. Or the parking brake pedal is down a little.


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## mkwl (Jan 21, 2005)

2COR517;991127 said:


> Matt - When you say both lights are on...
> Do you mean the Amber ABS light and the Red Brake light?
> 
> The Red Brake light could indicate a serious problem. Or the parking brake pedal is down a little.


Yes- almost everytime it has done this in the past- both lights have come on (red and yellow). Mechanic scanned it- threw a code for a lack of communication with the EBCM- I can't remember the code # off the top of my head. Pedal feels fine- brakes just fine as far as I can tell.

B&B- I have not had it flashed because all the dealers around me told me there is no such thing and it needs a new EBCM... to the tune of $1,200 or so... it usually (the light) goes off within a few days and it will probably come on again in the next few weeks or month when it gets wet or damp....

Thoughts? Also- could you advise which ground on the chassis under the drivers door is the one for the ABS? Could a poor ground here cause the 2 lights to come on and go off when it dries out?

As for the sensor issue- I doubt its that- the truck has 2 new front wheel bearings/hubs, and new sensors as well.


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## mkwl (Jan 21, 2005)

B&B;990886 said:


> Any time you have an ABS "issue" that temporarily shuts down the system the brakes should still feel as they normally do.
> 
> Did it happen right after you started the truck? Did you have the updated reflash done?


Yes, both lights came on right after washing the truck today (red BRAKE light, and yellow ABS light next to it).

I can understand why the ABS light would come on- but would the ABS issue also cause the red BRAKE light to come on? I'm sure the E-Brake is off also, if that helps  .

Just drove it back up to school- everything feels fine to me...


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## mkwl (Jan 21, 2005)

I'm not sure if it matters or not, but the DIC was also giving me a "Service Brake System" message... has always done this before as well, with the Red and Yellow BRAKE and ABS lights..

TRuck has been doing this on and off for about the last 6 months, seems to clear itself within a couple days... as long as it's an ABS issue I'm not overly concerned, but I want to be sure it's not likely tied in with my regular braking system... my mechanic assured me it was not, and the truck was fine to drive- this was in June, so far so good.


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## mkwl (Jan 21, 2005)

2COR517;991127 said:


> Matt - When you say both lights are on...
> Do you mean the Amber ABS light and the Red Brake light?
> 
> The Red Brake light could indicate a serious problem. Or the parking brake pedal is down a little.


They both come on and go off together, (one isn't on when the other is off, and visa versa)... so I'm assuming they are both because of an ABS code... and am assuming that it's the "loss of communication with EBCM" code...


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## rbi014 (Nov 6, 2009)

Had a 2005 Silverado with the same issues - whenever it was wet out, the ABS would go on and after it dried out light would go off. Local shop was able to pull the code saying it was on the front driver's side. Turned out the problem was at the connector from the hub to the truck harness. This is located by the upper control arm. 

Even though the connector snapped together properly, I accidentally discovered I could turn the ABS light on and off by gently tugging on the wires or pushing the wires towards the mated connectors. 

Cut the connector off the hub side and soldered the wires behind the connector on the truck side. Problem solved. Fortunately I left the connector on the factory harness because I did end up replacing the hub due to mechanical failure about 15000 miles later - but the ABS issue was solved.


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## t.i.b (Jan 17, 2009)

my 02 had the same problem. it ended up being the electrical connection under the master cylinder had come unpluged and got pack full or snow and crap. cleaned it up and plugged it in and every thing is back to normal. hope this helps.


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## Newdude (Dec 4, 2006)

if you get the re-flash done, #04-05-25-005A is the tsb. For some reason though, GM Service Info will only recognize the numbers, not the letter A, so if you go, give them the numbers only before they think you're nuts.


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## mkwl (Jan 21, 2005)

Newdude;992369 said:


> if you get the re-flash done, #04-05-25-005A is the tsb. For some reason though, GM Service Info will only recognize the numbers, not the letter A, so if you go, give them the numbers only before they think you're nuts.


Aaahhh I could believe this! I'm not going to have a chance to get it into a dealer for the re-flash before the storm tomorrow night-Wednesday, but will clean the ground, and take it for the re-flash sometime next week.

Should I be concerned about any other systems on the truck (like the 4x4) not working with these lights on?

Thanks,
Matt


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## golfmanres (Jan 3, 2002)

brad96z28;692899 said:


> If the light is on it has a code for sure.


This is not true. I had my l;ight on for two year untill i was ready to pull the tire and find the wire for the sensor on the driver side was cut and it was rubbing behind the hub and metal sheild that protects the caliper. I replaced the sensor for $80 at the dealer and put it on and out went the light!


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## 2COR517 (Oct 23, 2008)

That's some interesting logic....


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## mkwl (Jan 21, 2005)

2COR517;992617 said:


> That's some interesting logic....


What's that?


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## 2COR517 (Oct 23, 2008)

Not you, I was talking about golfman's logic. 

I'm sure B&B will let you know if both lights on will affect any of the other systems.


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## B&B (Nov 4, 2006)

2COR517;992652 said:


> I'm sure B&B will let you know if both lights on will affect any of the other systems.


He did, via returned PM. :waving:


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## 2COR517 (Oct 23, 2008)

See, I'm so smart


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## mkwl (Jan 21, 2005)

2COR517;992652 said:


> Not you, I was talking about golfman's logic.
> 
> I'm sure B&B will let you know if both lights on will affect any of the other systems.


Oh, okay lol

I PM'd B&B- I've got the all clear, should be okay with it until I can get it looked into further.


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## mkwl (Jan 21, 2005)

B&B;992703 said:


> He did, via returned PM. :waving:


B&B to the rescue again (helps to calm my nerves as well )!


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## Newdude (Dec 4, 2006)

mkwl;992432 said:


> Aaahhh I could believe this! I'm not going to have a chance to get it into a dealer for the re-flash before the storm tomorrow night-Wednesday, but will clean the ground, and take it for the re-flash sometime next week.
> 
> Should I be concerned about any other systems on the truck (like the 4x4) not working with these lights on?
> 
> ...


sadly enough, I have had the same thing happen to me (abs and rbwl on, svs. brakes) leaving a local Lowes one day. I scanned it with a tech2 and got...nothing. After reading the bulletin, I am strongly considering the re-program to prevent future scares. 

As for affecting anything else...I would say no. The night it happened to me, my abs functioned properly along with my brakes, and everything else was fine. What cleared it for me was a shut down and restart. Haven't seen it since...(knocks on wood)...

tsb: #04-05-25-005A

#04-05-25-005A: Advance SI Resolution - Antilock Brake System (ABS) Light On, Service Brake System Message on Driver Information Center (DIC) (Reprogram Electronic Brake Control Module (EBCM) - (Sep 28, 2004)

Condition
Some customers may comment that the ABS light, Service Brake System message comes on intermittently during initial start-up. The condition does not cause a DTC to be stored permanently.

Cause
The cause may be a timing issue related to the cranking/starting of the vehicles. It appears that the condition is more likely to occur on vehicles with diesel engines, though it can occur on vehicles with gasoline engines as well.

Correction
Reprogram the EBCM with TIS software version 7.5, released July 26,2004 or newer. Refer to Service Programming System (SPS) (SI Document ID #1451930).

When I saw the tsb on Service Info, it also mentions that this applies to 2500/3500 trucks with RPO code HVY (2 inch body lift).


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