e38 6L80E to 4L80E help

[greasess]

I'm swapping a 2008 Pontiac G8 from a 6L80e(t43) to a 4L80e(T42). The wiring is done and I'm able to read/write to the new t42 controller. The new t42 is out of a 2008 chevy 2500 work van that was controlling a 4L80E. From what I've read it seems like I have to change the OS on the E38 ECM to something that's looking for a t42 controller. If possible I would like to retain the tap shift feature. I know the t42 used in the 2008 Pontiac grand prix has this feature using a 4T65E. The current E38 OS is 12624402 and the old t43 was using 24243170 and the new t42 has OS 24239927. What OS(s) should be used for this? Any help or advice would be greatly appreciated.

[koolky]

The 08 Grand Prix runs an E67 ECM with OS 12618164. I'm not sure if any of the platforms that run an E67 and have the correct communication options to work with the G8 modules.

[ScarabEpic22]

PCMofNC sells a swap harness for this exact scenario, not sure what they do for tuning around it: PCM of NC 6l80e to 4lxxe conversion harness/ (https://www.pcmofnc.com/product/6l80e-to-4lxxe-conversion-harness-3/). Shoot them an email or call, they may be willing to sell you the TCM and/or tuning they use to make it work.

The 12618164 ECM OS was apparently a widely used 2008 E67 ECM OS. The TrailBlazer platform uses it too and the 24239927 TCM OS is the factory 08 TrailBlazer OS for 4L70E. The Express Vans use the same OS for 4L80E, but are E38 based with ECM OS 12617631.

[greasess]

The 08 Grand Prix runs an E67 ECM with OS 12618164. I'm not sure if any of the platforms that run an E67 and have the correct communication options to work with the G8 modules.

I didn't know it was paired with an E67. I'm sticking with the E38 in the car now. What I was getting at was that the t42 does support tap shift in some vehicles. Some options are there for it in the 24239927 OS that's in the t42 already. I have the signal wire for tap shift that went from the bcm to the t43 going to pin 10 on the t42 like it does on the grand prix. I don't know if this will work but it seems plausible. Maybe I'll have to use a hex editor to look at the differences between the GP t42 OS and others.

I full flashed OS 12617631 to the ECM(found the compatibility list). I applied the VATS patch to it and I guess I have the settings correct for that. I haven't worked with many E38s and I'm starting to see that VATS issues aren't as simple to deal with as they are on an LS1B. The car won't crank when I turn the key. The dash shows the correct gear so at least that's working. What PIDs should I be monitoring when I'm trying to start the car?

Thanks for the info ScarabEpic22 but I'm trying to learn how to do this.

Thanks for the replies.

[koolky]

Log ENGR - Power mode / starter status. Even if you made a mistake doing the VATS patch I believe the car should still crank, fire and stall a few seconds later. My guess would be a configuration difference between the G8 and the file that you loaded (truck or van?). I'd have a look at the ignition wiring and ECM pin used for the two platforms. Also, with the key in the run position you could pull the starter relay out, bridge the 2 terminals to force it to crank over.

[greasess]

I went back to OS 12624402 that came from the factory in this g8. Turning the key does nothing. Jumping the starter relay with the starter relay coil in place so the ECM sees the right amount of resistance just turns the engine over with spark and no fuel pressure. If I do all of that while jumping the fuel pump relay it does start. When it does start, the dash lights up like a christmas tree. The dash also tells me that the engine has been immobilized while it's running fine. I guess that's because the original OS isn't looking for a t42. I have also tried all of this with x1 pin 52 grounded or connected normally. I updated my V2 firmware and 7.5 and 8 tuning and flashing software. I tried applying the VATS patch and full flashing it again. I have tried everything I can find in this forum that has to do with this problem. I really don't know what else to do. One of the guys I know that has HPT keeps telling me to buy him the credits and he will fix my vats problem. When he reads the tune HPT says that vats is enabled. It seems like the two pieces of software go about disabling vats in different ways so that might not mean anything. If anyone can help point me in the right direction I would really appreciate it. 2323723238

[greasess]

I just tried a 2008 Vette 6 speed OS because I saw that it worked for someone else. This time, the fuel pump gets power without jumping anything. I did the vats patch and full flash with all the other options that go along with it. Nothing much happens when I turn the key. When I jump the starter relay it does start for a second or two and then dies. That sounds more like a vats problem to me. The display on the dash still shows park, reverse, neutral and drive correctly."FIN" I have an alternate theory that this is related to the COVID 19 outbreak. If the car is infected, will a full flash fix the problem? I'm having trouble finding any PIDs to do with viral infections. Should that car be using a specific kind of intake filter for screening out viruses? I haven't taken it to any strange gas pumps. I live in Florida and we are currently under "lockdown". My family and I have everything we need but we are going a little stir crazy. Due to the alcohol shortage I learned how to LS1B (P59) swap a makeshift distillation rig. I'm using the fan control output and a coolant temp sensor to regulate a hot plate under "THE STILL". I'm able to datalog the still's temp and it's very consistent. I'm not really sure how much ignition timing this thing wants but so far I'm not seeing any detonation. I also have a 2 bar map sensor installed so that If I build more that a few kpa of pressure it kills the heat. Has anyone made a cax file for still protection mode?

[greasess]

Nobody has any ideas?

[greasess]

23242 I took this screen shot with the key turned. The ECM isn't turning the starter on. Any suggestions would be great.

[koolky]

Looks like the ECM might not be getting P/N input (log show inactive). You could log RVSDH to see if 'Trans Range Not Park'.

[Hooter]

Ya gotta get a Turbo 500 still.... that'll ease up your EFI Live....
Ive done many e38 T42 conversions here in Australia, but I get my fair share of problems with them.
Firstly, this combo was available in the first 6L 2004/5 VZ Commodore but only with 4L65e, which is easy to modify the harness so that the 4L80e will run on a 4L60e tune.
We also, in the same year models have a HSV version using the LS2 engine with 4L60e with T42
Not all T42's are the same....
It will only work with matching PCM and TCM's and O/S's
We do not have TUTD for these, but am keen to know if its possible....
6L80e's have the Park Neutral switch inside the trans, which feed from pin 3 on the trans plug to X1-01 and this wire also branches off to the start relay ground.
The 4L60e has this wire in the selector switch assembly on the side of the trans on the selector shaft... (at least they do here is Oz), and the 4L80e doesn't have this that I have seen anyways...
So ideally, you need to run this grounding wire through your PK/N switch to ground, and also on the ecu side of switch, to the start relay for it to function properly.
But for now, just try grounding pin X1-01, also something to watch here, is that this is grounded before turning key on, otherwise this gives a no start as well.
With the start circuit and relay, you must have everything such as canbus and all trans wiring perfect because the ecu will no give the all clear to the start relay to turn on.
I eliminate this circuit in conversions because of this, and switch depress clutch off and disable start diagnostic as well as switch to ground in the software.
I may still have the diagrams for T42 e38, but not sure if they will work in your Pontiac (VE Holden Commodore), because the ecm you use wont match your bcm, hence xmas tree on dash...
The big problem with these early e38 OS is they seem to be very reliant on the other onboard ecu's and seem to spit the dummy really easy.
Personally, I would stay with the 6L80e, as they are awesome, once you get your head around tuning them for hp