Unhooked Battery, now it won't start- Please help! *SOLVED*

[George B]

So make it 13 minutes between off/on/start cycles. Or maybe try in succession the procedures documented in the first 19 YouTube videos that address similar problems.

Without a high end two way scan tool, it is going to be a kind of blind man’s bluff thing.

It is possible it isn’t even a theft deterrent problem. It could be a fried liftgate control module, BCM, PCM, crank relay, etc. etc. etc.

Building on this logic: I wonder if the liftgate module shorted and is pulling the comms bus down.
Without a two way scan tool, oscilloscope and wiring diagram this will be hard to find. Work your way upstream from the liftgate motor.

 

[wsteele]

Building on this logic: I wonder if the liftgate module shorted and is pulling the comms bus down.
Without a two way scan tool, oscilloscope and wiring diagram this will be hard to find. Work your way upstream from the liftgate motor.

I agree. The lift gate logic is tied into the whole "do we let him start this thing up" code. It might be something as simple as resetting that module (or the BCM) so it says everything is jake with the lift gate...

A Tech 2 would be invaluable in this circumstance.

Edit: Maybe check the thread below out and see if one of us that own a Tech 2 is nearby. A long shot, certainly, but not any more of a long shot than doing many of the YouTube procedures guys document to get their no start trucks back online.

Tech 2 Owners Map

There are quite a few members that have a Tech 2 and there are always people who wish they had one to use so I thought I would post this thread to try and help each other out. If you own a Tech 2 and would be willing to help out another forum member that might be local to you then post up your...

www.tahoeyukonforum.com

 

[Scrapman]

Building on this logic: I wonder if the liftgate module shorted and is pulling the comms bus down.
Without a two way scan tool, oscilloscope and wiring diagram this will be hard to find. Work your way upstream from the liftgate motor.

Do you think unplugging the liftgate module might let it crank? Or possibly re-set something?

I was replacing the latch assembly with the battery connected because every video I watched on how to replace it never mentioned unhooking the battery. It seemed like a simple plug and play. When the assembly started whirring when I plugged it in, I unplugged it and then unhooked the negative battery cable.

Finished installing the latch, hooked up the battery and got the no start situation I'm in.

 

[George B]

Do you think unplugging the liftgate module might let it crank? Or possibly re-set something?

I was replacing the latch assembly with the battery connected because every video I watched on how to replace it never mentioned unhooking the battery. It seemed like a simple plug and play. When the assembly started whirring when I plugged it in, I unplugged it and then unhooked the negative battery cable.

Finished installing the latch, hooked up the battery and got the no start situation I'm in.

Yes, undo whatever you did and see what happens.

 

[wsteele]

What it has sounded like from the beginning is when you connected the actuator and it was running, you disconnected power and the state the module that was calling for the lift gate actuator to run was left in that state. That state may be incompatible with starting the truck, TD or otherwise. If you can clear that state (may be as simple as disconnecting things that are lift gate related and reconnecting), you may get back the privilege to start the truck.

 

[wsteele]

Another thing to try would be if you have a liftgate switch on your console , flip that switch off, maybe the PCM won’t check the liftgate status with it off.

 

[89Suburban]

Plug the old one back in? Isn’t the positive terminal usually the one that gets disconnected?

 

[Scrapman]

What it has sounded like from the beginning is when you connected the actuator and it was running, you disconnected power and the state the module that was calling for the lift gate actuator to run was left in that state. That state may be incompatible with starting the truck, TD or otherwise. If you can clear that state (may be as simple as disconnecting things that are lift gate related and reconnecting), you may get back the privilege to start the truck.

Yep. I just don't know how to clear it. I have taken the new actuator back off, re-installed the old one; Tried to crank- Nothing

I also stuck my hand through the opening for the jack and unplugged 2 of the 3 wire looms going to the liftgate module. (I couldn't figure out how to get the bottom one unplugged) and still no change. I may try to get the last one unplugged again.

 

[Scrapman]

Plug the old one back in? Isn’t the positive terminal usually the one that gets disconnected?

I could be wrong, but I was always taught that DC current in a vehicle flows from - to +, and to take the - off to work on anything. I wish I would have heeded that lesson before installing the latch.

I also put the old one back in and it didn't change anything. Thanks for the idea.

 

[wsteele]

I believe people are told to disconnect the negative to reduce the chance of sparks, shorts, etc. while disconnecting.

From a DC theory point of view, you need both sides to make a circuit.

Do you have a liftgate power switch on the console? And if so, have you tried turning it off?