abs and brake lights come on whenever i go over a small bump ..please help.. on 2003 Chevrolet Avalanche 1500

abs and brake lights come on whenever im going over a small bump or pot hole it also says to service brake system when i already serviced the brakes... my speedometer isnt working also..i dont know what it could be please help.......

by in West Hills, CA on March 06, 2010
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2 answers 4 comments
ANSWER by , June 25, 2010
also having problems reduce engine power light coming on and the a/c going off
COMMENT by , July 26, 2010
My 2004 Avalanche is doing all of these things as well. The dealership is telling me I need different modules replaced but I'm not convinced. All of theses things go hay wire at the same time and only when I hit a bump in the road. Any solutions?
COMMENT by , February 27, 2011
I have a 2002 Avalanche and my ABS and Brake light come on when I hit a bump or just driving. I had a diagnostic test done and was told I needed to replace the ABS switch module.
COMMENT by , May 25, 2013
Hi, I'm having the same problem you all described, to a point that I can't really drive it anymore. Has the problem been fixed for any o you? Mine (at 2004) has been in the dealership for a while and they can't figure it out... I'm pretty scared to see the final bill and a nil diagnosis!
COMMENT by , September 20, 2014
i have a 2002 avy and have gone thru all thats been said on this site.have been told its my ground wire in back of intake manifold.have checked it and appears to be good however there is a lot of dirt and grease on it.don't know if that makes a difference.am in the process of putting a ground wire from frame to engine block in hopes that could be a fix.am also taking my starter down and cleaning up,a lot of corrosion on terminals.there appears to be a ground on it also.so thru all this talking with a lot of people its a ground issue.hope this helps.
ANSWER by , August 28, 2015
This a common problem, if your Avalanche tries to shut off / turns off more often on a road bump, your locks go off, ABS and Brake lights come on, ac turns off and blows hot air after, your truck has a bad ground. Looking front of the engine, check ground wire at rear of engine (black/white) between trans and engine breaks off main trans harness. Its on the back left side of the black engine cover left side of it. Taking off the engine cover gives you extra room to work with. I think the bolt is a 10mm, clean the bolt and the engine bolt whole area, and re wire or solder the bolt clamp. This will solve your ABS, Brake light, engine shut down, AC shut down. This ground impacts all this systems.