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ABS and Brake Light on and B2647 and B2585 code
03-09-2012, 09:43 PM
Post: #1
ABS and Brake Light on and B2647 and B2585 code
I Have 2000 Chevy Silverado 5.3L V8 Extended cab that has 2 problems 1. The ABS and Brake light come on at random sometime it will come on right away other times it might not come on for days, I changed the Speed Sensors rebooted the computer still same thing comes on at Random. 2 I checked my codes in computer and I have 2 codes showing B2585 and B2647 what do they mean? I noticed that my Day Time running lights don't work any more neither do my fog lights which i looked up are all controlled by the BCM.

Thanks for your help in advance
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03-09-2012, 11:56 PM (This post was last modified: 03-10-2012 12:17 AM by Rupe.)
Post: #2
RE: ABS and Brake Light on and B2647 and B2585 code
The first code is for the parking lamp circuit. It seems to be non specific so I would double check to see if they work manually before going further. The second code is for the light sensor (on the dash) with automatic head lights.

I found this link showing ALL of the GM body codes. Quite interesting and I hope I never need it personally.

http://www.dieselplace.com/forum/showthr...p?t=428288

As for ABS codes, you will need a scanner that can read ABS codes, which is another category from body codes and engine codes. In my experience when both the ABS light and the brake warning light come on intermittently it's a bad EBCM along with the pump assembly. IOW, it may be both parts and they are not cheap. I bought both this week from the dealer and it ran me about $1,300. Don't forget to order the special screws that hold it together. The old ones seldom come out due to rust. It's not a fun job either because of where it's mounted and the five brake lines, which may also be rusty. Don't forget that at 12 years old the bleeders may be stuck / rusty and you simply can't do the job if you can't bleed the system afterward. IOW, made damn sure this is the problem via a proper system scan before hand!

BTW, the ABS codes in my case indicated a bad EBCM relay (part of the $700 control module) and another code said the pump motor was no good. (pump assembly aprox $600) I had seven codes total and my parts were discounted. (I have a small fleet)

Edited to add: the ABS module will not reboot even if the battery is disconnected for a week. Codes in storage may go into "history" but they don't clear, although the dash light may go out till the problem crops up again. Problems within the EBCM are hard codes because those parts are non service items. IOW, all you can do is replace, there is no repair.

Let us know how you make out or if you have any more questions.
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03-10-2012, 12:03 AM (This post was last modified: 03-10-2012 12:06 AM by Garner.)
Post: #3
RE: ABS and Brake Light on and B2647 and B2585 code
Both of those codes are related to the lights & the BCM. I don't have any specific information right now as to where to start looking for the problem. Just by reading the definitions I can see that if the computer "Thinks" that the parking lights are on, the DRL's are not going to come on. If the "Ambient Light Sensor" is turning the parking lights on the DRL's won't come on.

Here's the code definitions:

B2585 - Park Lamp Control Circuit Malfunction
B2647 - Ambient Light Sensor Circuit Low (BCM)

I have a '99 Chevy Tracker. I simply didn't like that the lights came on when "They" wanted to. I found that I could lift the Ambient Light Sensor out of the dash, unplug it, & I then had normally functioning headlights that "I" turn on & off. You might want to see if that is possible with yours? It could buy you some time until we figure out the problem?

If the ABS light is coming on there should be some codes stored for that. If you aren't using a "High End" scanner you likely won't find those codes. Most "Code Readers" won't access the ABS, Air Bag, or Transmission codes.

What Speed Sensors did you change?
Also, how did you "Re-Boot" the computer?


Without having codes it could be a long process looking for why the ABS light is coming on. I have found that random occurrences usually means that a wire is starting to break from flexing with the steering or suspension. It could also be a wheel bearing going out. Without codes, check the wheel bearings carefully. You can check each Speed Sensor with a DVM looking for A/C voltage as a helper spins each wheel. The faster the wheel spins the more voltage it should produce. (!!DON'T stick your finger through the rim to spin the wheels. When your finger hits the brake caliper it won't be pretty!!) If the wiring connectors are corroded; even a little bit, they can foul the signal. If all wheels check OK; same voltage for about the same speed of spin, you have to move to the EBCM (Electric Break Control Module.) Unplug it, look at the colors of the wires to determine the wires for each speed sensor, & spin them again checking for voltage. You can also do a continuity test from the Speed Sensor plug to the Module plug. Have a helper wiggle the wires while you look for a fluctuation in the gauge. You might see now though where a code that tells you the problem is in the Right Front can save a ton of time.

Please keep us posted to your progress.

I see Rupe & I posted together.

Thanks for using the forum,
Garner

Interested in Mining? Look here: Coal Mining, PA
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11-14-2012, 08:20 PM
Post: #4
RE: ABS and Brake Light on and B2647 and B2585 code
I have the same truck with the exact same problems. Have you found out what the cause was?
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11-15-2012, 06:38 AM
Post: #5
RE: ABS and Brake Light on and B2647 and B2585 code
Unfortunately, this person never got back to us with the "fix." I would suggest that you read over the posts for tips and then please get back to us. Letting us know what you find could help someone else!

Posting your details; like exact code numbers, could also give us more clues to try to figure it out.

Thanks for using the forum,
Garner

Interested in Mining? Look here: Coal Mining, PA
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11-16-2012, 09:03 PM
Post: #6
RE: ABS and Brake Light on and B2647 and B2585 code
(11-14-2012 08:20 PM)aussiedog61 Wrote:  I have the same truck with the exact same problems. Have you found out what the cause was?

I regards to code B2647 where my headlights would stay on all the time and the DRL's never kicked in, it was indeed the ambient light sensor switch on the dash. I purchased a new one at the dealer (only $14) on installed it myself. Works beautifully now.

Install instructions are here: http://www.truckmodcentral.com/forums/sh...php?t=1654
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11-16-2012, 10:39 PM
Post: #7
RE: ABS and Brake Light on and B2647 and B2585 code
Thanks for posting the "Fix" along with all of the extra information that could help others! So few people take the time to follow up. We are glad to hear that you were able to repair it yourself.

Thanks for using the forum,
Garner

Interested in Mining? Look here: Coal Mining, PA
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