If when you did the "fuse thing" you removed and replace one fuse at a time, there could be a parallel path going through two, or more, fuses. The reason I'm thinking this way is that if it is not going through more than one fuse than it would isolate the problem to the battery side of the fuse block. Reduces the search considerably.

Not really sure what to make of the battery reversal incident. That will exercise a bunch of non-standard electrical paths. Vehicles are not known for there electrical protection circuits.

Question: What is the current draw? milli-amps? The magnitude of the draw may lead to some idea of maximum wire run between the battery and the short/load. This is a long shot but....

Don't mean to be insulting but one of the things I find useful is to keep a troubleshooting note book and record all of the steps that I take and the resultant measurements/observations. This has many times help me avoid redundant effort. I myself am cursed with a write-only memory.

Believe me I appreciate doing this sort of thing in hot and, in my area, humid conditions. We're supposed to go near 100F and 65% this weekend sometime.

Again good luck!
GD

 

Grey Dog,
Your answer is the best, no insult detected. I have isolated the circuitry inside of the cab, my drain is from the ECU to the engine compartment. The wiring in the cab is easy and all exposed, on the other hand there is a Big Fat section of harness behind the distributor which will require me to remove it to have access enough to remove the loom and electrical tape so that I may trace individual wires.

I check the voltage drain, not the amperage drain, I took the positive cable off of the batter and put the red probe of the VOM meter to the positive terminal on the battery and the black probe of the VOM meter on the positive cable and it is indicating the maximum voltage from the battery.

I believe that if a car wiring is good it should have a one to two volt drain with the clock and other devices that run when off disconnected. the wiring insulation seeps a little and the older a car is the larger the seepage is. That's what I learned in automotive class in the '80, perhaps that isn't so with newer cars?

I keep some stuff written down but I also use my digital camera extensively. About that parallel path thing, I understand now, take them all out to get the real status, I'll take a pic of what fuse goes where, quicker than writing it down.

I am in Phoenix and we been having near three digit temps at night any how I have a widget on my desktop showing the weather in Dublin California where it's fifteen or twenty degrees lower and I want that, I want to move somewhere near there but this truck is holding me here.

100F + 65% ? doesn't that equal 165 degrees? I am sure it does.

I haven't dilly dabbed with that truck in about a couple of weeks but I want to, "Geterdun"

 

There is HOT and then there is D**n HOT after that it don't matter.

Another thought just rattled through my brain. Remove the fuses one at a timeuntil, with luck, the drain disappears. Than start replacing them, leaving the one that supported the current out. This may cut down on the effort to find the second one if one exists. I'd do the same with the second one. Leave the first two out and continue replacing the rest and so it goes till they're all back in.

Now you'll have to figure out what's in common on those fuses.

The other possibility, the drain never goes away, gets you back to "It's somewhere between the fuses and the battery" scenario.

Hope some of this helps and again good luck.
GD

 

I have isolated the wiring in the cab off, the problem is from the Electronic Control Module to the engine compartment also keep in mind that I have all the devices on the engine disconnected.

I wonder how to tell if the ECM is damaged, the drain does not show when it is disconnected. The truck still runs though. This kinda say the ECM is damaged but not exclusively.

 

I'd start with the ECM fuses (My 2011 Chevy has several.) and see if those are supporting the drain. This would at least confirm which feed to the ECM is misbehaving.

The really tough nut to crack is: Do you have the correct ECM for the harness? Vehicle electronics are notorious for subtle changes year to year, engine to engine and even production date to production date. Establishing what you have and how it relates to your engine and the unknown harness may be next to impossible to establish. Also, up until now I believe you've assumed that the fuses are correctly assigned and identified, this may not be the case either. (Due to the harness issue) The engine code and the ECM markings should be traceable through GM to make sure they match up.

Assuming that things ran normally at one time and you have the correct ECM installed, I'd go with a replacement. If it's the wrong ECM, I think I'd try to check out differences between it and the correct unit. (Through schematics, primarily verifying input/output pin assignments.)

We're getting into the realm where e-mail troubleshooting/diagnosis has reached its limits. Don't know how helpful I can be from here on out and please understand that I am just providing ideas that may or may not lead to a solution. This is an area where I am not well versed in the specific details. I am, however, experienced in troubleshooting electronics. So please take my advise for what it is.

Good luck!
GD