Converting a 2000 GMC C6500 U-haul Box Truck over to P01 (0411) PCM

[SurfRodder]

Hello All,

As in title, I have a 2000 ex-U-haul box truck -- 7.4L Vortec L21 backed up by an Allison AT545 -- I am in the process of swapping over to P01 PCM using a 2002 C6500 tune. I have already done most of the pin swaps -- I need to modify a few after a fail to crank upon first attempt. I discovered several discrepancies in my pin swap sheet between "standard" 0411 swap info and MY2002 Factory Service Manual (FSM) pinouts I think I'll have it running next time I head out to where truck is stored. I have a hard copy of MY2000 C6500, MY2002 C6500, and MY2002 B7 FSMs for PCM pinout comparisons. I can post my spreadsheet later once I've verified some things.

I am working with another forum member local to me in the PacNW and have bugged another one that did similar on a friends' truck with a manual trans a few years back for his tune and wiring info.

I think the 2002 C6500 with 8.1L and Allison "tune" files are also for AT545 (less electronic) Allison, but it looks like the B7 series might have the 1000 (fully electronic controlled) Allison as the FSM for B7 shows a lot more pins for "Transmission Range Switch Signals," etc. and the C6500 pinouts only show "Automatic Transmission Modulator Relay Control"/"Shift Relay Coil Supply Voltage"; "Park/Neutral Position Signal"; "PCM Serial Data"/"PCM Class 2 Serial Data (Allison)".

The only other thing I wanna verify is that "TAC Throttle Actuator Control Serial Data" = "UART Serial Data".

Anyway, looking forward to getting this project knocked out finally!

[SurfRodder]

Ok, so answering the TAC Serial data = UART Serial Data questions:
https://www.lt1swap.com/99-02_vortec_pcm.htm
indicates that the UART Serial Data is for DBW only, so it follows that this is indeed the same as TAC Serial Data.

I am going to re-attempt the repin and make final consolidated notes on my spreadsheet before uploading it here for posterity.

[dave w]

I'm curious to learn more about the '0411 conversion.

I converted a 1999 L21 / 4L80E to the '0411. The '0411 conversion was fairly straight forward conversion because the schematics for the L21 were from a 1999 K3500, and the '0411 schematics were from a 2002 Express Van L31. The L21 and L31 used the low resolution 4X crank triggers (which still uses a Distributor with a Cap and Rotor, not coil-on-plug like the 8.1 engine has). Both the L21 and L31 were Drive-by-Cable throttle bodies. I modified a 2002 L31 flash for the L21 0411 conversion.

s-l400.jpg

What was the original PCM part number for the 2000 GMC C6500 U-Haul Truck? I'm guessing a "Black Box"?

Black Box PCM.jpg

Does the Allision have a separate control module?

Transmission-Control-Modules-TCM-Allison.jpg

IMG_2767-rotated.jpg

[SurfRodder]

What was the original PCM part number for the 2000 GMC C6500 U-Haul Truck? I'm guessing a "Black Box"?

It uses the same oddball PCM as the 97-98 Corvette: 16238212 and is indeed DBW, CoP, and cam sensor instead of dizzy setup. Cam sensor plugs in where the dizzy should be.

Does the Allision have a separate control module?

It does.. I havent put eyes on it, but remember reading it had one a while back and that also makes sense with what inputs it gets from the PCM.

It will make more sense once I verify and post the pin swap spreadsheet.

Your project is definitely less common that most! At least the 4L80E code seems readily available. I am 95% sure the Allison stuff I got with a "flashmasters" PCM I bought a while back that was flashed for a 2002 Topkick 8.1 with (reportedly) AT545 Alli 4 speed should work with the 7.4 fuel and spark tune I got from a guy who did this on a manual trans truck a few years back should at least get it up and running / driving, but I wont know for another few days.

[dave w]

Thank you for the clarifications.

The 8.1 vs. 7.4 have different firing orders.
8.1 firing order: 1-8-7-2-6-5-4-3
7.4 firing order: 1-8-4-3-6-5-7-2

The firing order is "Hard Wired" to the PCM connector. The coil-on-plug wiring pins in the PCM connector will need to be moved to correct the firing order.

The attached information is for a 2002 2500 HD 8.1 / Allision

Gearhead-efi link for 2002 8.1 / Allision Drive-by-Wire .bin files (post #10 looks like a close match): https://www.gearhead-efi.com/Fuel-In...rPro-Bin-Files

[SurfRodder]

Thanks for the links...I saw that 8.1/Alli file the other day and have yet to compare to what my local tuner pulled from the 0411 I purchased.... wouldve (probably) saved some cash had I seen that sooner. There's also a 99 bus one I saw on here last week that looked promising for other things to try in case what I have doesnt work for some reason.

Re:firing order, Id noticed that the pins were different compared to the generic 0411 pinouts ive seen, but wasnt tracking firing order was changed...since Im using 454 tables loaded into the 8.1bin, do I need to wire it up like an 8.1 or do I swap 7&4 and 2&3 from the 8.1 FSM pinout?

Thanks again!

[dave w]

I would swap the 7 ~ 4 pins and 2 ~ 3 pins.

It would be a good plan to correct the cylinder bank assignments too.

Capture.jpg

[SurfRodder]

Copy, thanks...I will add it to "the list."

[dave w]

Possibly the information in this thread will be helpful: https://www.gearhead-efi.com/Fuel-In...173#post104173