1999 Chevy Express 3500

Diesel 6.5 18k miles

I bought this from my town auction, threw a battery in and it started right up.

Drove it approximately 100 miles and security light came on solid. At first, this did no effect the operation of the vehicle.

One day I started it up about an hour after driving it and there was no power to all lights and accessories but it started up and I was able to drive it home.

Once I parked it, I turned it off then back on and all my accessories were back on. The car would not start and battery was weak to crank. Battery was brand new.


I then bought a new battery for the 2nd battery underneath van. I didn’t realize it was there and hoped that would take care of problem. It didn’t.

After weeks of research, I was coming up with the passlock security system was stopping the van from starting.

It will crank strong with both batteries, start for a half second but not stay on.

I replaced the passlock key housing and key with cylinder. I did the relearn but no dice.

I then bought “New Rockies” passlock bypass for lots of money thinking that would do it but still no dice.

My latest move was to call for help. 3 different mechanics tried to hook up their code scanners and were not able to connect. The port was powering up the scanner but saying not able to connect.

Checked all fuses and they are good.

Checked fuel pressure at fuel rail and gas flowed when key was on. Loosened fuel injectors and no gas.

From what I’ve read, passlock disables injectors so this seems to be happening.

Maybe the ECM failing is what’s causing it not to start. I’m so stumped. What would cause the code scanner to not be able to connect the Ecm?