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Electrical Dilemma - Dash going crazy - Lost Headlights & Fog Lights

crwalkerasla

Well-Known Member
Messages
312
Location
Corinth, MS
Hey there folks,
I've got a real head scratcher here.

Symptom: When you first crank the truck, every warning light on the dash comes on, Speedo & Tach jump around, fan, windows, and lights don't work, and truck runs rough for about 30-seconds. After that the warning lights go off, engine plains out and purrs like a kitten... until 6 weeks ago. Then the headlights hi/lo and fog lights went out.

The old man at AutoZone who gets referred to for all things electrical, listened to the symptoms, and checked a manual, then told me that it all seems to electrical items controlled by the Body Control Module (BCM), and that I should check it to see if it had any evidence of getting wet. It had.

I tried cleaning all the contacts and re-seated it with dielectric grease, but that didn't correct the problem. Checked the headlight fuses and relays, they were fine. Replaced the BCM, and had it taken to GM for a reflash - All the same issues are still there. Just prior to all this beginning, it was in the shop getting a new (stouter) alternator, transfer case, and front differential. I have recently sunk a ton of money into this and I still can't drive it. Patients are wearing thin.

Any ideas what it could be?
 

crwalkerasla

Well-Known Member
Messages
312
Location
Corinth, MS
One other thing, it only happens the first time it's cranked each morning. The rest of the day, it doesn't have the warning lights, starts normally. Except for the headlights.
 

alrock

El Diablo
Staff member
Messages
10,442
Location
Scottsdale
Have you tried a different battery? Wondering if low voltage is causing this. Also, this started with a new alternator? I don't know my electrics well, but could that be a factor, maybe with an issue with the voltage regulator?
 

Mr_Rich

Well-Known Member
Messages
636
Location
High Desert & Santa Maria
Mark your ice cube relays and start switching them around. It almost sounds like a sticking contact that loosens up. There are a bunch of those things in the fuse box and they are a fail/ marginal item.
 

4speedfunk

Well-Known Member
Messages
4,212
Location
Tardville
First & foremost...try new battery cables.
Next, take the main fuse box loose and look underneath it. This is a common corrosion area. Pull the big snake-head connectors off the fuse box and check to make sure they are properly seated. Look closely inside them, as a bent prong can cause this issue. Same is true at the BCM, TCM, and PCM. The connectors are a horrible design, and bent prongs are very common. It only takes one prong to make the vehicle go nuts.
I would reinstall a stock alternator too.
 

Traxx

Well-Known Member
Messages
682
Location
PNW
I would def remove the fuse box and inspect the connectors for bent pins. Can't even guess how many times I have had to fix that for people who removed it for repairs or to add things.
 

crwalkerasla

Well-Known Member
Messages
312
Location
Corinth, MS
Thanks to ALL! I have asked the shop to start with the Battery Cables, but not sure if I want them cleaning the pins. I'll do it myself.

Been doing more searching and thinking that there are multiple (compounding) issues going on. There is/was a body panel leak that would leave a puddle in the passengers floor board, unless the return air vent was closed. For the past 2 years that has prevented the issue, but apparently that is not working anymore. I have read about a "YAW SENSOR" that is located under the carpet and is tied to the ABS, traction control, & about 1/2 the lights on the dash. Does anyone have any knowledge of this? Honestly, I didn't know it existed until now.
 

rascole

Well-Known Member
Messages
2,580
Location
Bellflower, CA
It my be a pain in the arse but it is always better to try fixing one thing at a time when troubleshooting a problem. Then you exactly what the problem was and the battery clamps are a great start.
 

Traxx

Well-Known Member
Messages
682
Location
PNW
Well if you have a water leak on top of the bcm that would certainly be the first thing to fix otherwise you will always have problems.
 

crwalkerasla

Well-Known Member
Messages
312
Location
Corinth, MS
Well, the leaks were finally fixed today. The cowl vent had been cracked in a wreck. It is now sealed off. Now have the new BCM wrapped in plastic as an extra just-in-case measure. Back to the dash lights and headlight issues.
 
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