P01 vs P59 for GMT400

[Thelochnessmonstah]

I'm putting together the kit I need to do a ECM swap on my '99 GMT400 truck.

Is there any pressing reason why I couldn't use a P59 1mb ECM from a van with IAC control in lieu of the 512kb P01 0411 that everybody seems to use for that swap? I searched on here and found a low res L31 tune from a P59 equipped Mexican GMT800 truck, so I'm at least broadly aware that it should be possible. Has anybody done it? Is there some good reason not to?

[SS2win]

I've been working toward doing that swap but not dedicated the time for it yet. There are just a few changes to be made, 02 sensors the big one. Isolated ground on the P59. do it and report back.

Someone else please chime in with more infor if you have it.

[Thelochnessmonstah]

First things first, I need to get my mitts on the '99 GMT400 black box to 0411 spreadsheet. I dropped a PM to Lextech, but I'm not sure if he's around here much these days and I sure don't want to harass the poor fella across a bunch of enthusiast sites.

Once I can get that, my plan is to cross-reference the P01 pinout with a P59 pinout and see what specifically is different. I've heard, as you mentioned, that the o2 wiring is handled differently, but it'd be nice to have a definitive list of what changes between the P01 and P59.

Hoping someone's already forged some of this trail, but if not it looks like it's up to me!

[SS2win]

Yeah it's been done a bunch of times already. It's not bad from the perspective of the pinout changes. Adding the wire for the 02 could get complicated depending on how "factory" you want it to be.

[GMPX]

I'm really digging somewhere I haven't been for a long time but if I recall not all P59's are the same either. Some of them are missing certain output driver packs so some output functions do not work.

[aaronc7]

https://www.lsenginediy.com/comparing-gen-iii-controllers/

That's good info referencing what part/service numbers have what output driver packs etc.

I recently did a P01 to P59 swap on my 2003 Corvette. I did just like you said, I referenced a 2003 vs 2004 pinout (2004 Corvette is P59). In my case I only had to move 1 pin, for alternator control circuit.

On P59 the O2s are grounded to the PCM, but you can also simply disable a few DTCs and it works fine (that's what I'm doing right now).

[SS2win]

Sounds like you got lucky there... my 2001 SS is going to be a bit of work. I'd like to retain the O2 functionality so I'll be running wires.

[aaronc7]

Just to be clear, the O2s work fine using a chassis ground for the heater circuit. P59 just allows the pcm to monitor the heater circuit directly. If I was already running a bunch of new wires I woulda done it too, but I didn't feel like digging into it when the rest of the project was so simple.

[SS2win]

So did you use the stock O2 as well? never thought about it that way...

[aaronc7]

So did you use the stock O2 as well? never thought about it that way...

Yes, I didn't touch the O2 sensors or the wiring at all. I looked at the 2004/P59 O2 sensors for my car and it was a different style connector and everything, so I decided I would try leaving it as is and see what happens. The associated codes are P0135 and P0155 "heater performance".

I read something about having the O2 being grounded at the PCM allowed the PCM to keep the sensors at a constant temp to make them more accurate. But I wasn't really able to find any real info or data to tell me how much improvement or if it would be worth the effort etc. So I just left it as is for now...no issues or gripes so far.

If you're already going to be doing a bunch of wiring work, might as well knock it out while you're there IMO. But if it's going to be a pain or extra effort, I don't think you're gonna miss out on anything/much by leaving the wiring/sensors as is.

[SS2win]

10-4... thanks. I'm soon to give this a try.

[THEFERMANATOR]

The only real issue I see you running into is your fuel gauge. 98+ gmt400 gas trucks run the fuel sending unit to the pcm, and it in turn runs the fuel gauge. With an 0411 you use an express can fuel system as it used the sane fuel gauge setup, but I don't know if any p59's that use this style fuel gauge setup? If you have hptuners they have the fuel gauge tables mapped out to make it work(several on the fakebook ls swap page have done it), but efilive doesn't have them available, so you would have to find/build .cax files, or run a fuel gauge interface module. I have been contemplating going from my p01 0411 to one of my p59's to play with e85 on my 99 l31.

[hquick]

Any updates on this guys? contemplating doing 0411 to P59 swap also.

[SS2win]

Any updates on this guys? contemplating doing 0411 to P59 swap also.

Well I never got around to doing it. One day perhaps, but there is now a boost OS based on 12216125 so I'd probably go that route first.

https://pcmhacking.net/forums/viewtopic.php?f=42&t=7482