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2000 Silverado Z71 4x4 5.3L 480k+ miles w/ GM rebuilt motor and trans
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You may end up pulling shrouds and skid plates, but I doubt you'll need to pull the radiator. Pulling the headlight housings and the grill does open up a lot of visual space, though.
 

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Discussion Starter · #22 ·
I will check to see if I can access wiring without pulling radiator. I don't have access to a lift, so It's hard for me to get under the vehicle and do any repairs due to my age. The grille and headlightrs are already out, so that part is done. I'm trying to find out where the blue signal wire originates- don't know if it comes directly from the switch, or goes thru the fuse panels before or after the switch, and also which fuse panel. Thanks for the reply- it's appreciated.
 

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Most BCM circuits, and I think the turns/signals circuits are included, will have 3 inputs.
  • 12v through a fuse,
  • the trigger circuit, usually a ground signal,
  • the load to a load ground.

The 12v goes to a pin on the BCM cable connector. There will be many of these, some hot all the time, some only hot with key on.

The trigger circuit is the human interface, or the automatic interface. Turn the headlight switch to headlights on, a ground is placed on the trigger wire to a pin on the BCM connector. An automatic trigger input is the daylight sensor on the dash, when the daylight fades, the sensor becomes a digital switch, passing a ground signal to the BCM on a connector pin.

The load is the light being turned on. One side of the light is grounded at the socket, the 12v comes from the BCM. When one of the triggers is present, the electronics in the BCM acts like a switch and toggles the fused 12v to the connector pin that is wired to the load.

I used the headlights as an example in the case of the signals, there is a timer circuit that pluses the digital switch, causing it to turn on and off at a predetermined rate.

The dark blue wire should be connected to a pin on the BCM connector.
 

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Discussion Starter · #24 ·
Wow- sounds like Greek to me. So what you are saying is the 12v signal should be turned on and off by the BCM. Is that correct? The 12v hot from the battery (or starter) loops around behind the engine and is nowhere near the signal wiring which runs under the radiator support to the fuse panel under the hood. I took the fuse panel on the fender well apart-separated the upper and lower parts- looking for corrosion- everything looks ok. I get so confused now when I try to figure these things out- I never used to get that way- I was a pretty decent mechanic before I had 2 strokes and a heart attack-my heart is only pumping 30% of what it should- maybe that's affected my brain also- or the strokes did-or both. I now have trouble figuring anything involved out, but I try. Can't
really afford $149 per hour at the dealer, but I'm so frustrated trying to figure this out I may have to bite the bullet and take it there. I'll try again to figure it out tomorrow- I'm just flustered now! I appreciate you and the others who have made suggestions trying to help solve the issue. 12 years ago before my health took a dump I stood a chance on fixing this. At 71 yrs guess it's above my skill level now. Thank you all !!!!
 

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Bondo, sorry to hear about your health problems.
Just take your time and we'll help you though this, it's solvable if you have the time.

Edit:

Yes, the BCM turns the 12v on and off
 

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Discussion Starter · #26 ·
Bondo, sorry to hear about your health problems.
Just take your time and we'll help you though this, it's solvable if you have the time.

Edit:

Yes, the BCM turns the 12v on and off
I'm contemplating cutting the blue signal wire as it comes out of the underhood fuse block and goes to the light.. If the light stays lit, then it's shorting somewhere from there to the light. I have solderseal connectors to put it back together. Any comments?
 

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I can't guarantee the blue wire your looking at is part of the signal circuit, just because it's blue
 

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Discussion Starter · #28 ·
It's blue with a tracer which matches the signal wire- hey I'll try- can't only have an extra splice!
 

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The dark blue signal wire should not have a tracer
 

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Discussion Starter · #30 ·
I believe I have the right wire, but will probe it with a test light to be sure before I "operate". thanks for keeping me straight
 

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Discussion Starter · #31 ·
it's the only blue wire that goes to the light plug- it's on both headlight plugs and functions correctly on the driver side, but evidently the wire coming from the fuse box is only for the driver side lamp. I don't know where the passenger side gets the signal- the more I try to figure this out the more I get confused. I do know the wire crosses over underneath the radiator- guess I'll have to pull the convoluted tubing apart and try to figure this out. so confusing to me. I'll keep in touch- thanks
 

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Discussion Starter · #32 ·
I give up- going to take to the dealer and pay the $149 per hr. rate- Hate to, but have too many other things to do and it's beyond my mental abilities to figure this out. I've already spent too much time and accomplished nothing but getting frustrated! Thank you to RayVoy for attempting to solve this issue with me.
 
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