The DLC wire pictured in post #77 gives you the ability to self diagnose using the DLC connector under your hood. If correctly connected, you jumper two pins in the connector and it will cause a light on your dash to blink. The frequency of the blinking identifies various problems.
Specifically, the blinking light will be the light on the subtank switch. So you have to have it wired up and everything in place to be able to use it to diagnose the circuit.
Can somebody tell me which plug(s) have the wires running from the ECU in the back of the cargo area?
A, B and C are the three plugs I reference that all have the donor wires from the BACK OF THE TRUCK. Each truck is different for whatever reason so it hasn't been well documented "plug 1, pins 2,4,6,8 etc). That's why you have to get into the rationale of understanding the diagram. This is not plug and play.
Same question, can somebody tell which plug(s) have the wires from the sub tank sending unit ?
The easiest way to confirm this is to have someone ground out the yellow/red wire at the subtank ECU connector over to the frame using a short wire. Then go up front in those three plugs, disconnect the two that are plugged in and start ohming out all the yellow/red wires with a voltmeter. The one yellow/red wire that beeps is the wire coming from the tank (because its grounded out). Its either yellow/blue or yellow/red.
Several narratives mention connecting to the "charge light on the combination meter". What the he!! is that ???
The fuel transfer ECU in the back would like to see a signal from the charge/alternator light bulb that lights up when the battery is weak or alternator is failing. It wants to be able to stop a fuel transfer in that case. You don't need this right now so skip it.
Where do I tap in to get 12v to the rear ECU? Where do I tap in to get 12v to the rear sending unit?
You tap in to the 12V in the driver' side fusebox. I know you don't think you can read schematics, but you need to follow me here:
If you look at the wiring diagram back in post #1, at the bottom in the lower middle section you'll see the "fuel tank changeover switch". On the lower left of it you'll see a yellow wire leaving pin #4. It says it goes to the "Gauge" fuse, which is in the driver's fusebox. That's where you get 12v+ for the front switch circuit. The rear system already has 12V on it in those three connectors you are messing with. How do we know this? Because in looking at that same schematic, you'll see leaving the upper left of the ECU connector box in the middle of the page a black/red wire headed to the fusebox. Its already in the side harness and runs through one of those three connectors up to the fusebox. Via that existing wire and power source the sending unit is already powered.
