Engine ignition problem

[Fowler]

For a friend of a friend

 

2008 Chev Silverado 1500 crew cab 5.3L. 290k km.

 

Recent work:

 

1. Transmission swap last year, no issues.

 

2. Ignition cylinder tumbles drilled last year due to sticky keys. Problem fixed no issues after.

 

Driven up until about six months ago, when it stopped starting, no turn no crank. Just suddenly stopped starting.

 

Battery good, and no issues with power to fuse box, or to truck itself. All electronics fine, no Anti-Theft engaged.

 

Truck was towed into local shop and investigated with no success.

 

Most electrical grounds and lines have been inspected cleaned tested, Fusebox initially determined to be culprit due to corrosion, so new fuse box installed, power and grounds at relay. Fuses have been tested and swapped, all working fine. Can't manually engage relay for engine crank, fuel pump, etc. New ignition switch installed; neutral safety switch ok. ABS and airbags unplugged; OnStar unit unplugged. Scan tool found ignition to read crank but no signal from PCM, tested wires from ignition to fuse panel to PCM, wires are ok. *Possible PCM failure*

 

So, I decided to tow truck to dealership. Dealership did some investigation and re-coded keys, fuel pump wasn’t engaging, fuel pump fuse (20A) was missing or not working, replaced and the truck started. Dealership recommended to replace ignition cylinder and have new keys reprogrammed, but Truck STARTED and running so refused. Re-coded spare set of key and gave the truck back. I drove truck over the highway with no issues running smooth. turned truck off and on, restarted multiple times, no issues. Problem seemingly fixed.

 

The next day, the truck will not start again, exact same issue. Back to square one.

 

*(SEE VIDEO ATTACHED) I can be started with the key only if I disconnect and reconnect the main power supply, either at the panel or battery. The initial contact with battery to fuse panel seems to engage the injectors and fuel pump and you can immediately turn key and it cranks and starts.

 

I’ve started this truck multiple times now over the past couple of weeks with this method, with the key, by literally disconnecting and reconnecting the battery terminal power until the injectors engage, then key turns and fires up. Truck can stay on with gas applied to pedal and keeping engine revved, but loses power thereafter and shuts off. No diagnostic codes detected with use of last scan tool.

 

FUSE PANEL is good, FUSES AND RELAYS checked and good, ECM is good, NEUTRAL SAFETY SWITCH is good, IGNITION SWITCH is good, BATTERY is good (new terminals), 12v CABLES ALL SEEM GOOD, Most wiring has been inspected and cleaned, most if not all grounds are checks and cleaned, STARTER Works, FUEL PUMP working. ***PCM possibly the culprit, however because we can start the engine with the keys by using the technique described above. However at this point I’m suspecting it has to be some sort of comms issue between the ignition, the Body Control Module and the PCM, and we “shock” the system by disconnecting and reconnecting the main power at just the right moment and are able to start with the key in that instance, but not as normal.

 

Unfortunately, I feel like this is a bit out of my wheelhouse at the moment, as I am not a mechanic nor have ever seen a problem quite like this. Is it a matter of getting access to a computer and trying to re-code the keys or PCM? can the keys be re-coded without a computer? I'm just not sure of what steps to take next.

 

WHAT IS PREVENTING THE TRUCK FROM STARTING WITH THE KEYS, BUT NOT WHEN ALL THE CONNECTIONS ARE MADE TIGHT?

 

I’m offering $500 to anybody who can perform an exorcism and successfully diagnose and start my truck with the keys, reliably.

 

This truck ran smoothly, then it stopped starting, then the dealership got it started after 3 months of sitting, only to drive it for a single day, park it for the night, and have it stop working the next day.

 

If somebody is handy with truck repair or electrical issues, or has some experience and think they may be able to get it going I will buy or provide any necessary parts, consumables, and beer.

 

Thanks, community, for any insight or advice.