Hello. I am currently building the 5.3l LM7 in my 2000 GMC Sierra 1500 4x4 and have just installed the Fitech Ultimate LS +750HP kit with transmission controller on the truck.

While installing their wiring harness I noticed it wasn't going to be a plug and play like I was told. I called Fitech and explained the situation and was now told it will not work in my truck because the factory PCM controls so many other components of the truck.

My question is wondering if there is a way to disable the engine and transmission controls from the factory PCM to allow full engine and transmission control to the self learning Fitech system without compromising the cruise control, a/c and HVAC, air bags, abs, etc...? Any help is greatly appreciated.

This is the 4th post you have made about the same thing. Please, make only 1 post per same topic.

Sorry. New to this thought it only posted once.

Might be, but it would be difficult. I looked up the Fitech and it looks to be a LS-swap solution for someone wanting to put a LS in an older vehicle without all the gingerbread like cruise control, a/c and HVAC, air bags, abs, etc.

Biggest thing I see as a problem is the cruise control. For the factory CC to work, the PCM needs to know how fast the vehicle is going from the VSS in the transmission, then use that information to tell the CC module what to do.

HVAC is BCM. It might work with PCM disconnected from engine and transmission.

Air bags have their own module, but I believe it needs to know the vehicle speed.

ABS might work with PCM disconnected from engine and transmission.

SCV on the radio will probably not work with PCM disconnected from engine and transmission.

I think the gauge cluster will be a big problem.

It seems a re-evaluation is in order. It sounds like you want this vehicle to be what it is plus lots of horsepower. Is that generally correct?

If so, how much more power do you want?

Can that be done some other way besides a Fitech Ultimate LS +750HP kit ?

Yes that is correct. I was hoping to retain the modern electronics (gauges, abs, c.c., air bags, etc.) while converting the engine and transmission to the Fitech self learning system. I think it can be done "mostly" with the exception of the gauges in which I decided to make a custom panel with AutoMeter Ultra-Lite gauges.
I just got off the phone with Summit and they will charge me a 10% restock fee for the Fitech kit and I will just order a different intake, throttle body, injectors, rails and then just reprogram my PCM to work with the mods. At least that way I can retain the factory components and achieve the desired horsepower. To make it work would be far to much work in the long run. The factory harness and reprogrammed PCM will be far easier to deal with if problems arise.

Thank you for your insight on the situation.

A couple last questions for you. What do you recommend for the PCM to work for the mods?
And what do you recommend for a truck intake, throttle body, injectors and rails? My intent is to get around 500hp and 450ft lbs torque. It'* a daily driver. It is also set up for boost in the future once finances agree.

Thanks again

I agree. You tamper with the CAN system on these vehicles, EVERYTHING takes a dump.

PCM., find the popular GM 0411 PCM, Its far better at tuning than the black box version. (HPTuners)

If you are looking for an extra hundred ponies or more, stop with the nickle and dime piddly ****.
A. Exhaust. This thing is choking on the stock exhaust.
B. Cylinder heads
C. Cam
D. Injectors
E. Bigger intake.

All in that order. Don't ask us for what brand does what, or whatever. We don't know. You will have to research all that on your own, experiment with what you can get your hands on.

And above all else, you get what you pay for. STAY AWAY FROM THE CHEAP CHINESE ****.

And canned tunes. NEVER 'can' tune.

Yeah, what Mike said.

450-500HP from injectors, TB, and intake is optimistic, especially on a 2000. That'* a 57%-75% increase.

Your current injectors would be enough for an intake upgrade. You might see 300HP doing that. Bigger injectors come in when you are getting lots more air into the process, which an intake by itself won't do.

To summarize: What Mike said above.

. . . and to do that you may as well yank the engine and go through the bottom end while you're at it.

Thanks again! I will look for the GM 0411 PCM.
My truck currently has a GM 4896 PCM.

Lol, no nickle and dime here! Here is a list of some of the performance mods.

ARH 1 3/4" Stainless Steel Long Tube w/ y-pipe attached to a Borla catback system

Trick Flow GenX 205 Competition ported, 58cc CNC Chamber cylinder heads, 1.7 ratio roller rockers.

Trick Flow Track Max camshaft, cam is degreed and has an Intake Duration at 050 lift of 220.5° and an Exhaust Duration of 234.5°. Intake and Exhaust lift at .560in. Intake centerline is at 110° ATDC, Exhaust at 117° BTDC

Underdrive pulley system.

Reevaluating the intake, and injector situation. So many choices out there.

Any recommendations on PCM? HP Tuners? EFI Live? Or buy an PCM set up with my specs? Built tons of old school engines an have owned LS engines for years. This is my first LS build in this kind of depth.

The most I've done to an LS prior to this was a Diablo Sport Predator programmer, cat back exhaust, AEM dryflow cold air, and electric fans.

Thanks again.

Ah. This would have been good to know up top. It would have saved my chin from hitting the desk when you wanted 700HP on a stock 2000 5.3 with an intake and some injectors. :O

This is out of my league. We mostly troubleshoot nearly-normal stuff here. Someone here might have some input but I know we almost never see anything like this in our pages. I don't think anyone here has anything against it, just doesn't happen much around here.

From what I've read, the LS motors are great for adding power. I saw a magazine just a few months ago where they pulled a junkyard LS with a bazillion miles on it, put different heads and intakes on (the untouched bottom end) to see how much power they could get out of it and god 500+HP at one point if memory serves.

It would be interesting to see how yours comes out.