Again, look at what the link is saying. The ground needed may be only coming thru when cranking the engine. In this case you may well need a new ignition switch. https://www.rockauto.com/en/moreinfo...24090&jsn=2287

 

put new ignition switch, same problem. GM computer says bcm is getting no power. Changed everything, programmed to truck and still same problem. Crank attempts to start, kills fuel saying it’s not receiving signal to enable fuel. But security light comes on as normal and goes off. Is there a wiring problem causing this? I literally drove to the store came home shut off locked truck with keyfob and come out the next day to this nightmare! Key fob with new battery doesn’t work, power windows and locks interior lights cluster back lights none of these things will work.

 

I am sorry for the problems, I really am but without being there to test, I am just guessing based off of your info. Did you replace the ignition switch from the info I gave you 2.5+ hours ago or had you already replaced it before and did not say so?

I would also look to see if there is a bad wire or connection at the starter solenoid mounted at the starter. You made this statement in the beginning: " Truck turns over, attempts to start and immediately dies."

That tells me that as long as you are cranking it wants to start but when you release the key after you think the engine started, then you lose power thru the ignition side of the circuit.

There are 2 big studs and a small stud at back of solenoid. See if there is any problems with the wire at the small stud on back of the solenoid.

Also, see if will crank and start in neutral.

 

I’m not trying to complicate this, but to figure this out, clarity is important. No scan tool, factory or otherwise, is going to state that a module has no power. A scan tool has no way of determining that. What it will state is that there’s no communication with a module, an issue that could be due to lack of power, but could also be due to faulty grounds or a short/open on the communication circuit.

Although the linked article has some valid points, I’m not in agreement that a problematic battery cable is to blame because no diagnostic process (according to what I’ve read at this point) has led to that conclusion.

System communication problems are relatively easy to diagnose but require patience and skill with a meter. If you’re not comfortable performing diagnosis, you’ll spend a lot more time and frustration trying to figure this out. If you don’t know how to use a meter but are willing to learn, it’s not that complicated. The primary difficulty isn’t in testing the circuits but in accessing the test points, especially in the cab as they are usually in the dash and aren’t easy to see.

That said, here’s a couple of things to try before you start ripping apart the interior (if you haven’t already).

1) In the early 2000’s, some GM vehicles had a fault in the communication circuit in which the passenger door window/lock switch would short out and pull the whole data circuit down. The typical result was a no-crank no-start and that the scan tool couldn’t communicate with any module; however, it’s an easy thing to rule out just in case. All you have to do is remove the passenger door switch and unplug it, then attempt to start.

2) Since the ignition switch has been replaced once already, verify it was installed correctly. There was a TSB issued by GM regarding the switch installation and how it could be incorrectly indexed to the key cylinder. Since you stated that the window will work while cranking, this is a possibility. The easiest way to verify is to rotate the key cylinder to each position and verify functions. With the key off, no accessories (such as the radio) should turn on. In the accessories position, the radio, windows and HVAC should work, etc.

3) Try a battery disconnect and a hard reset. A hard reset just means disconnecting both battery cables and clamping/bolting them together or connecting them with a jumper wire. This allows current flow which will discharge the battery backups for all the modules which will clear all active fault codes. Leave them connected for at least an hour, then reconnect to the battery positive first.

If none of these help (including inspection of the wiring harness under the driver seat as I posted earlier), you’ll have to access the BCM for diagnosis of the circuits.

 

you’re correct it won’t communicate with the bcm. GM computer communicates with everything but the bcm. The truck cranks, actually starts for maybe 3secs and then just dies. Along with all the other issues it’s having. I don’t understand how I drove it the day before and while parked over night something went wrong I’m so lost here! The ignition switch was swapped rite before I messaged you. Still same problems. I’m starting to think I have a wiring problem, is there common wire that you know of that would cause all my issues??? Thanks

 

z06corvette1983 at g mail
im having trouble getting your msgs on this forum

 

Turn the on without trying to start the ignition

 

I have.Everything is normal security light goes out. I’ve also done the (handshake). Please email directly? Mine is z06corvette1983 gmail
and switch had never been replaced until this current issue I’m having, original switch has been reinstalled as of now.

 

These are current codes

 

So found out BCM is not getting constant power or any power for that matter. Ran a wire from fuse box straight to BCM and it fixed everything... but it doesn’t really fix the issue which is a wiring issue somewhere that I can’t find!