OK, we have a lot going on so lets try to break this down. I wish I had a simple explanation but I dont. No single failure explains all of this.

The truck starts and then dies. This can be many things but the basic question is what quits: Fuel pressure, injector function, ignition/voltage, a key sensor, the computer. The easiest to check are fuel pressure and voltage to the ignition system. After that it gets more complicated. This behavior is consistent with a passlock problem where the computer lets the truck start but then disables the fuel injectors. Normally we would watch the security light but your dash is messed up for now so we should do the fuel pressure and leak down test and watch the ignition voltage on the coil or ICM pink wire during a shutdown. The schrader is the fuel system connection on a metal tube at the top of the engine: The security light never comes on, correct?



If this is a passlock problem that involves the ignition switch module, the BCM, the engine computer and the class 2 digital data lines. This is literally the only problem you have which MIGHT involve the engine computer. The only thing this shares with your other problems is the BCM and possibly the ignition switch and not for all of them. Thats why I dont agree with a new engine computer and all of this is not even explained by the BCM.

In some cases the BCM and not the BCM control a given circuit in parallel. Lets start with the dash function back lights since there is no BCM in most of that one. For the majority of the dash back light bulbs including most of the instrument panel, power goes to the headlamp switch and if you move that switch to manual park or manual headlamp then power goes through the thumbwheel and on to most of the back lights. So either there is no power or the ground(s) are messed up. There are three separate grounds for these simple circuits. If the steering wheel controls and the instrument panel lights and the headlamp switch backlight dont work when the headlamp switch is in the manual on position then its not the grounds. Then the best bet would be to remove the dash panel and get some voltage measurements.

There can also be a problem with the instrument cluster but I am trying to avoid that for now.

The fact that your parking lights stay on with the relay removed says that the part where the BCM controls those lights is not the problem and its the more traditional simple control part thats the problem. SO either: the dash headlamp switch is messed up (again) or there is a short to power or a ground problem. Probably the easiest way to proceed on this one to pull all the parking light bulbs and then check for power at a bulb socket. This removes the possibility of a bad ground and backfeed and looks to see if there is always power on those lines with everything turned off. If you are going to go into the dash first then skip this for now because that dash switch may be the problem.

Liftglass: The dash button and the keyfob go through the BCM and we can check for proper output from the BCM at the liftgate relay but before we go there, there is a third circuit on some vehicles to open the rear liftglass that does not involve the BCM and that is a rear liftglass button if so equipped. If you have one and that also does not work then there is a separate issue from the BCM. Do you have a rear gate button or key switch that operates the rear glass? If so and that circuit also does not work then it can be a few things but this includes the drivers door lock cylinder which you are also having problems with. If you do have this circuit and it works OK then this may be the easiest way to condemn the BCM. We would start at the liftglass relay and work our way back.

Radio: The radio gets it power from three different fuses and then uses the G201 ground on the right side of the dash, the BCM is not involved. Since removing the radio to check for power is a pain, other things go to that G201 ground. Does your right side exterior mirror work? What about the right side door and window functions (cylinder switch, door handle controls? They also use the G201 ground.

Interior lamps: I'm not addressing this one yet because its the most complicated of the bunch. The BCM, inadvertant power relay, switches, ...

This is a lot but the problems are a lot. I cannot see any one cause for all of this and I tried. Logic would say the truck ran fine then it sat and then it has all these problems, what is that single point of failure? I'm not joking, I wonder if this truck was hit by lightning? Another thing could be load dump damage from charging/jumping/bad battery but that usually only affects computer modules. I normally dont like the parts cannon but given your situation If this is all overwhelming and you want to fire the parts cannon then that would probably be the BCM but I cannot guarantee this would work without more testing. That and this would not fix your parking lights and dash back lights for instance. That and the BCM is under the dash.

I wish I had a less complicated set of observations. I'm pretty good at reading schematics, diagnosing electrical problems and finding the root cause but this is a big set of issues.

Let me know what you are thinking and how you want to proceed. I am here to help in any way I can.


George

 

I forgot to ask about one of the most basic items after a long period of storage. Have you pumped out and replaced the gas?

George