PCM program

[Gapper_ca]

I have a stock 96 L56. i have read on here at times that some have changed the PCM to a 99 L65 PCM. my ? is how hard is this to do. is there lots of programing? what about the security feature that is on the 99. will this affect the remote starter that i have?

i have seen where there is a 30 to 40 hp difference. i am curoius as a freind has a very large salvage yard. and just might have the parts there.

thanks

[autocrosser]

I don't think you can use the 99 program in your 96 truck. I believe the 98 and up trucks had the security feature and you can't defeat it in the PCM unless someone has figured a way around it. It looks for something hidden in the wiring of the truck to read. Been there done that!

[diesel65]

The problem you will have when you swap in a 99' program is the computer will be looking for a Passlock signal, With no signal the engine will attempt to start but won't stay running.

Your steering column does not have the ignition key assembly with the Passlock sensor and you need a different module that is under the dash.
Also there is a couple of additional wires that is connected between the steering column and the module.

I did that conversion and it wasn't easy.

You are much better off getting a 97' computer with the F engine program, then you won't need to worry about the security feature.

[Gapper_ca]

ok sounds about what i figured.
was not to sure about the security thing.
oh well was just wondering thought that it might b a cheap way to get more hp with out a aftermarket comp.

thank you

[diesel65]

Gapper,
Try to get a computer out of a 1997 2500 series suburban or pickup, it is a cheaper way of getting a few more ponies out of the engine and not have to worry about the Passlock system.
If you do it, you will need to disconnect some sensors or you will confuse the computer.

[EscaladeDiesel]

I have a 1998 Suburban, and to my knowledge I do not have a passlock ignition. My key does not have the "Chip" and looks exactly like my 1997 Truck. Does the passlock not require a chip in the key or is that something else?

[AndyL]

My 99 doesn't have the chip either.

[diesel65]

That is the beauty of this Passlock system that the key does not have a chip, you could go and have a duplicate key made and not worry about the chip.
This version of Passlock came out in 1998 and all the parts to sense the key are in the ignition lock cylinder and steering column.

[Turbine Doc]

A 98 to 99 is what I did but I did have to do the pass lock learn for it to work correctly, I had a BD reflash Z-Ind PCM that I tried that never would learn and I had to send back I suspect it wasn't a passlock PCM, that is how I came across the 99 HD computer, I was looking for a cheap core to return, tried the 99 3/4 T junkyard PCM it worked and ran nearly same as another Z-Ind reflash PCM I finally got that worked. I returned the reflash, been running the 99 PCM for 2 years $125 Jy. vs $600 Rfl.

Now I'm working with Bill Heath to try his reflash, 1st time it didn't work I suspect theft learn problems, there will update when bugs worked out.