03 truck with 02 electronics won't start

[Dkatubi06]

i have a problem with my brother in laws truck guys. I want to make a long story very short and get to the point but explain it at the same time

6 years ago my brother in laws dually got caught in a flood
truck was totaled out and bought back, supposedly he or someone drained fluids replaced truck was started and ran- parked at his shop on higher ground

Fast forward to last year, truck is parked in same spot with weeds growing around it and a wrecked 2500 sitting next to it minus the motor and a-pillar
He comes to me and asks if I can swap everything out thinking he just wanted ECM Tcm and ficm he said EVERYTHING. So a week later, the 2500's body harness, fuse box, dash harness, cluster, taillight harness, steering colum, BCM, lower engine harness and upper engine harness are now sitting in the dually

Go to start, just cranked pumped them primer a ton finally got
It to start.
CEL on, low power, limp mode, sounds like it's running on 4 cylinders job complete he said he'll take care of the rest.
He calls me a week ago saying it won't start ( a year later still parked in the same spot) I go down I look around he said it needs a ficm I swapped him mine out of my 03 truc- won't start. I noticed it wasn't getting fuel from the tank so I hooked up a temporary bottle and lines also swapped in a good reputable hand primer and new filter ( old one seemed to not get hard at all) this one does after a few pumps

Me real question is will the 03 ficm in my Silverado work with the 02 platform?
The ficm out of his truck( the one I swapped out for mine has a date of 6 of 03 on it) he thinks someone may have swapped out his and replaced it I cant recall a date on the one swapped from the 02 2500 funny thing is the ficm he thought was bad workes in my 03 truck

 

[THEFERMANATOR]

All LB7 FICM's interchange. The sticker on them is different, but an 04 CALI one will swap into an 01 truck, and work. FICM's RARELY fail unless somebody shorts them out.

 

[RPM Motorsports]

If it's been sitting in the weeds like you say, I bet mice got to the wiring under the fuse box..., them bastards like that area along with the motor valley/CP3 area

 

[Dkatubi06]

Yes Russ it's been sitting someone suggested a crank sensor I just had the fuse box apart to check if someone messed with any plugs there all good. After the crank seniors I got no idea I may pull the glow plugs too see if he's got any leakers thanks for the information guys

 

[RPM Motorsports]

Truck will start and run without glow plugs. Get a scanner, check fuel psi cranking and cam/crank signal, that will give you an idea where to start. Is the dash showing that the VATS is on? Pic of a lock around a truck?

 

[Dkatubi06]

Security light flashes as normal doesn't stay on steady, it just cranks, I'm going to have to locate a scanner

 

[DAVe3283]

Normally the security light never blinks. It should come on solid for 1-2 seconds when you turn the key on, then again on solid for 1-2 seconds after it starts, then go out.

If it is blinking, you have a PassKey / VATS (theft deterrent) problem.

However, normally a VATS issue would result in a start then die condition, not just constant cranking. You might have a different issue. Either way, you need a scanner.

 

[Dkatubi06]

On my dually, the security light flashes until I start it, leave the door open, or arm the alarm. I figured since mine does it it's normal for his. I know a lot of gm gas vehicles will start and die if there's an issue with the theft. Seeing how the truck has been started since last year I doubt it's a security issue

 

[DAVe3283]

OK, see I am confused. The thread is titled 03 truck with 02 electronics. I figured that just meant the ECM & TCM, but the dash and interior was still an 03.

On 2003+, it does what I described. I do seem to recall the 01-02 trucks blinking like you describe. So I guess it depends on which dash/body computer is in the truck now.

And yes, a security issue results in a start then die, so there are other problems. Either way, a scan tool is needed to figure out why it won't start.

 

[Dkatubi06]

Yes everything in the truck NOW is 2002 wiring, computers, even the damn seat harnesses