ECM/BCM???

[xohcef]

So a few weeks after purchasing my d350 I've had a handful of wiring/electrical problems hop up and I'm getting frustrated and quick. I've had a handful of dash lights and gauges and what not sweep and light up and turn off and all kinds of sweet stuff all while the keys out and whiel the truck shouldn't be doing anything. Well, I thought it was the ignition switch/tumbler so I switched those out and still had the same problem. After debating and looking over all the visible wires I cannot find a ground wire or a short/open anywhere. With all the crazyness someone said it's probably a ground, especially if it doesn't make sense. I can only point my finger back to the BCM. There's 3 different part numbers for this BCM 56024859, 56026858, and 56029101. What I want to know is how interchangeable are the 3? I've also removed the BCM from the truck and removed the cases to see inside, However it's all covered by a thick layer of silicone. What I'm curious about here is should I be able to see through it? Mine is very cloudy and I definitely can't. Has anyone had ECM/BCM problems and which direction if any can you point me in?

[Mark Nixon]

What year and trans is your truck?
The silicone in the ECM is semi opaque and will darken with age/heat.
Very, very rarely is it an indicator of condition, unless it's a blatantly obvious burnout spot, which is extremely rare.

Regardless of what you may think, check all of the grounds, the one from the battery to the core support, the one behind the head and, under the dash, the ones attached to the gold irridite plate to the right of the coulumn.

Also check the fusible links, which are near the driver's hood hinge, as well and any power connections at the battery .

In other words, fine tooth comb it for bad connections, because gauge issues don't stem from ECM issue.

Mark..

[Hansen01]

ground from battery to core support. That one does alot of funny things with gauges, blinkers, headlights ect.

[xohcef]

Truck is a 93 with a getrag. Thanks for some responses guys. I can say I've taken the core support ground and big ground cable off the block and sanded em clean and re installed them. I have not checked the one under the dash or behind the head. I've continuity checked all the links and looked for anything else out of the ordinary all over the truck I guess I will do that and check back in with you guys.

[xohcef]

Found the ground behind the head and cleaned it up like the others. Can you elaborate on the under dash grounds Mark? Specifically its location and what I'm looking for.

[Mark Nixon]

To the right of your gas pedal, attached to the (steel) inner dash reinforcement is a gold-colored plate where there are several wires with loop ends screwed to the plate.
They normally aren't corroded, but sometimes I have found them not quite tight.

Mark.

[xohcef]

Awesome Thank you. I tried a few more things last night with no luck so hopefully this does it

[Mark Nixon]

If you haven't already, look at the ignition switch connections for signs of hot insulation or other damage.

Mark.

[xohcef]

All looks well with the ignition switch, been cruising with the column covers off for weeks. I've already tried replacing the tumbler and switch itself. So I believe that's good. What I wanna know is exactly where the other end of this ground strap goes that I fouund dangling under the dash one part is hanging from a metal bracket just yo the left and behind the stereo. Mark, does the plate you're talking about have two studs on it? Is. It the same thing I'm talking about what the ground straps on?

[Mark Nixon]

If the "strap" you are talking about is a woven looking bare wire, it grounds the stereo to the same plate I was referring to.
That plate IS held to the main DASH frame with 2 studs and the stud on the side closest to the brake pedal usually has all of the grounds for the harnesses on it.
The other stud is where the radio strap you mentioned bolts to.

You might also check that the 1/2 inch bolts on the ends of the dash are tight, as well.
They are kinda' hidden near the kick panels (or "cowl covers"), at the ends of the dash.

Mark.

[xohcef]

Thanks for the response Mark, I really appreciate your help. Checked all the rest of the ideas and have had no luck. Aftermarket stereo so that should rule the ground strap out as the new ground was run to the same plate. Tried to tighten both the 1/2" bolts but they were both tight. Tried adding grounds and jumping existing grounds to new spots. No luck. At this point I'm ready to gut the truck of its wires and make my own harness for everything. Lights, climate control, cruise, turn signals, etc etc. I'm so bummed I'm having these problems. I just wanted a toy hauler to get my car back and forth to the track. Now I have 2 projects and I deffinitely can't drive the race car to work. Lmk if you guys have any ideas before I push this thing off a cliff.

[Mark Nixon]

Well, then it's time to do some accessory removal.
Unhook ANYTHING that is not stock to the truck, radio, amps, CBs, brake controller, etc.
Do it one item at a time until either nothing is left, or until the problem goes away.
It's quite possible you have some cheap POS that went bad and it's back feeding power where it's not supposed to be.

Another thing that HAS done something like you describe, and I've mentioned it before, is the fusible links.

I had one fry on my old flatbed once and when I hit the power window switch, the info center lights would come on!
Not long after I fixed that snafu, I replaced the whole under hood harness and no more of that crap!

Mark.