Electrical help needed badly!!

I'm having a problem with my 2000 Silverado 5.3 4x4 that I can't figure out. Bear with me here as it's a long description.....

When I ran over a bumpy road yesterday, the headlights began to dim/brighten then when the raod got smooth, they stayed dim and the message center showed the security light, truck still ran fine and the voltage gauge still showed over 14v even while the lights were dim. Then all these things started happening:
1)The LED that shows what gear your in went off. Gear LED's were still on, just the highlighted part went off.
2)Fuel/Voltage/Temp gauges all went to 0/empty
3)Security/Low fuel/Voltage lights began flashing in the security panel
4)Abs/Seatbelt/Airbag dash lights started flashing
5)Air compressor came on and won't shut off



I've had a slight problem with the security light in the past but it never did this stuff. I ran my AutoTap on it and got 3 codes:
P1626 - Security
U1041 - Loss of EBCM Communication
U1064 - Loss of Communications with DIM

Since it seems to start/stop doing this over bumps, I'm thinking maybe a bad ground or connection but I don't know where these modules are. Can anyone help me figure this out as it's driving me nuts and don't want to take it to a dealer unless absolutely neccessary.

Thanks for any help you can give!!

I had a similar problem with my truck, except mine would die, and it wouldnt want to restart. The only thing I did was replace the battery(not needed) and had the battery cables cleaned(corroded) and had everything tightened up. I dont know if this will help you any, but it is a low budget place to start. Good luck.

Thanks for the reply anyway but I don't think that's it(wish it was) because the truck doesn't die or run bad at all, and I can shut it off and restart it with no problem.


It just popped another code: U1301 Class 2 Communication Circuit Low Voltage

Low Voltage? Sounds just like a bad battery connection, loose wires somewhere, or just one ground. Do you still have the orig battery? Pull your cables off the battery, check the posts and clean them. Can't hurt to see if the posts are secure....

Good luck!

i would check the battery and the alternator, seems like that would cause what ur explaining.

check the blinker fluid while yer at it :naughty:

You may have to have the computer reset? I would start there, remove pos battery cable for like 30 minutes, then reboot!!! BBZZZZZTTT

Will give your suggestions a try today. Thanks

check the plug that plugs into the back of the instrument cluster for tightness and corrosion....

I'll give it a shot, can't hurt any.

check the blinker fluid while yer at it :naughty:

Well, resetting the comp did nothing but as far as blinker fluid, I'm gonna get some synthetic fluid here:http://www.kalecoauto.com/fluids.htm:D

It really does sound like a bad ground. There should be atleast one ground point under the dash, look and see if any point(s) have worked loose under there being it is affecting your dash instruments also. I had a simular problem on a 85 S-10 and it turned out to be a loose bolt on the ground lug for one of the ground wires under the dash.

check the plug that plugs into the back of the instrument cluster for tightness and corrosion....


Just tried that and same thing's happining. Gonna look for ground wires now.

Just tried that and same thing's happining. Gonna look for ground wires now.

while you are checking grounds i would check all the harness's and plug make sure nothing is unplugged or corroded and none of the wires are chaffed and cut.

Gonna check out wiring today. Looked over some of it and everything looks good so far. The truck only has 38k miles on it and has been taken care of well........can't believe I can't find this problem. I miss the old non-computer days!

My 2000 Intrepid had a similar problem. It turned out to be the battery. The battery in those cars is installed right behind the right front wheel well, and vibration had loosened a connection between cells in the battery itself. The car always started fine, and ran fine (no codes), but at night, after a bump the lights would momentarily dim. I'd really get the battery load tested somewhere, preferably someplace that understands how they are constructed.

The volt gauge is going to show you alternator output with the truck running, not neccesarily(? true battery voltage. I don't pretend to know how these newer vehicles are setup with all the electronics, but I have the feeling the battery is used as the actual source voltage for all electrical functions (like a voltage filter), and if this is the case, the alternator could be charging happily away (regulated at 14V), but the battery may not be giving the required 12V needed by the ECU. Hope this helps..........

Just got in from checking for grounds and found nothing loose/bad

Gonna swap batteries now and see what happens.

Well, battery didn't help. Here's another symptom of what it's doing. While it's idling in the driveway, if I turn the ac on and the blower above 3 the gear selector light goes out then after about 5 seconds the sec light comes on.....turn the blower down and the gear selector light comes on and the sec light goes off. Also if the engine is off but the key is on and I have the radio on, if I turn on the headlights and blower, the radio goes off....turn the blower down and the radio comes back on. And that's with either battery so it's not a voltage problem, at least from the battery, plus it'll still start with everything turned on.

I want to take it to a dealer but I have a feeling they're gonna have to trace something down and that'll spell "BIG BUCKS"

Any more ideas before I commit Hari Kari:)

Take it to an Autozone or Pep Boys or similar and have them check the alternator which they usually do for free. If the engine starts is one thing but if the alt is not producing a stable voltage everything acts funny. As you drop voltage the dash functions will be selectively shut off.

It's worth a try....

Maybe an exorcist????????? Sorry

Man, that all sounds FUBAR!!! The exorcist approach sounds like a good idea. Good Luck!!!

New movie in Pre Production: "The Exorsism of Dans Silverado" coming soon...........


Guess I'll take the alternator in next, although according to my laptop/Auto-Tap, it's charging at a constant 14.1v but why not try anyway?

Have them run it through the different RPMs and see if it stays where it should. :dunno:

Next go to the Tarot Card reader shop and have them give you a reading on the truck's life line. :banghead: .... :bricks1: .....