L67 swap PCM issue

[Quaraxkad]

I have a '92 Cutlass that I've just completed swapping in an L67 and 4T65e-HD. The engine and transmission are both from a 2004 Impala SS, and I also have (or had...) a PCM from another 04 Impala SS. I have an AVT-852 cable/adapter and RoadRunner (Moates branded TunerCATS). I can't get the car to run using the Impala PCM. I also have PCM's from a 1998 Lumina LTZ (which I was initially led to believe would be the best PCM to use), and a 2000 Grand Prix GTP. *Both* of those start and run the engine (after disabling VATS). The LTZ has a N/A 3.4L, the GTP has the same S/C 3.8L, and both have differences in the transmission that prevent me from using either of them for actual driving. Something about the 2003+ transmissions having fewer/different pressure switches. I've tried so many different configurations and bricked two PCM's (WinFlash occasionally crashes during writes), and can not get this thing running properly.

First thing I tried to do was read the bin from the 04 Impala SS PCM, disable VATS, and flash it back. After a few attempts to find the right value to disable VATS, WinFlash crashed and bricked that PCM. So I tried writing the SS bin to the LS PCM, again trying all possible values to disable VATS, eventually bricking that one as well. In any case with either of those two PCM's (pre-brick), the engine cranks, fires *one* cylinder, and then dies. I then found in Mitchell wiring diagram that the 04 Impala SS has one additional power wire labeled IGNITION, at C2-24 which is hot in ON and START. This is in addition to the C1-19 IGNITION WAKE UP that's present on both cars. C2-24 is not used in earlier years and empty in my wiring harness (which came out of a 98 LTZ). The Impala also has PCM CRANK PWR, a purple wire on C2-23 which is hot in START only, also an unused pin in my harness. I thought I had found the culprit in C2-24, unfortunately I didn't get a chance to test hooking up that new pin to B+ before bricking the SS and LS PCMs.

I'm not sure if writing one bin to a different PCM even works, but by this point I'm trying anything I can. So I flash the 04 Impala SS bin to the 98 LTZ PCM. Again, the engine cranks, fires one cylinder, dies. I hook up C2-24 to B+ and try again. It cranks, starts up and runs for a few seconds, and then dies. Which seems like a VATS issue, so I try all three values for VATS in RoadRunner, 0/1/2, and then all three values again with VATS Injector Disable Time changed from 4 seconds to 0. Changing injector disable time was the only way to disable VATS in the 00 GTP PCM, which I learned from a post on this forum. No matter what, the engine either fires once with C2-24 disconnected, or it runs for a few seconds and dies with C2-24 connected.

I'll attach my bins here, if anybody wants to poke around in them. Stock unmodified bins from all four of my PCM's, and Mod2 is the last version of the bin I flashed to the LTZ PCM.

Am I wasting time trying to get this LTZ PCM with Impala bin to work? Is there something else I might be missing? If any more information is required, let me know!

[dave w]

I'm thinking the 2004 Impala would PCM be the best option. I'll take a look at the 2004 files posted above with my TunerCats OBD2 software later, and get back to you.

dave w

[Quaraxkad]

OK, thanks! I'll start looking for another Impala PCM, and I'm considering buying HpTuners, assuming it's less likely to brick my PCM.

EDIT: Since I will have to buy a new one, should I only look specifically for a 2004 Impala SS, or would the LS be just as good assuming I flashed the SS program to it? They both had the same service number 12583827. Probably some other cars have that one as well.
According to RockAuto:

BUICK	CENTURY	2004-2005
BUICK	RENDEZVOUS	2003-2005
CHEVROLET	VENTURE	2004-2005
OLDSMOBILE	ALERO	2004
OLDSMOBILE	SILHOUETTE	2004
PONTIAC	AZTEK	2004-2005
PONTIAC	GRAND AM	2004-2005
PONTIAC	GRAND PRIX	2003
PONTIAC	MONTANA	2004-2005

[dave w]

I looked at both the 2004 Impala SS .cal files, posted above. Using TunerCats OBD2, the files look correct.

WinFlash has the option to flash using "PCM Recovery" which has worked for me on several occasions, but PCM Recovery is not 100%.

If your willing to risk the shipping expense, I'll try using my WinFlash PCM Recovery (pro bono) on the "bricked" PCM. You supply the .cal file to be flashed PCM Recovery.

Send me a Private Message for shipping details.

dave w

PCM Recovery.jpg

[Quaraxkad]

I did try the PCM Recovery option on both bricked PCM's, immediately after bricking and again after sitting unplugged overnight (or longer), and that didn't work. I don't recall the exact message, but I believe the status box said "Write Failed, Retrying" a few times and then it gave up. I did just try it again on the LS PCM, and it worked this time!! So now I have the Impala LS PCM flashed back to stock. Should I try again writing the SS Mod2 file I attached above? What is the correct value disabling VATS on this PCM?

I also forgot to mention one additional thing that may be important for my application. This is partially speculation, I don't know if it matters or not. I am using an earlier model external gear selector switch instead of the one that's built in to the transmissions in 99+. The two may or may not be electrically identical, which is why I'm unsure if any of this matters. According to this tech article (second paragraph under 4T65-E), a transmission that does have an internal "IMS" can be used in cars that originally had an external switch by simply swapping the external switch onto it. In this case, the IMS goes unused and the PCM reads from the external switch. But that article assumes you're using the stock PCM for that car, which would be programmed for the external switch. However, since I am now using the PCM from a 04 Impala (which has an IMS) instead of a 98 or earlier PCM (which have external switches), is there a difference in the programming between the two? Maybe just a flag that needs to be set? If there is one, I didn't see one in RoadRunner or TinyTuner.

[dave w]

I'm unable to provide good information, largely due to the fact I have not had the opportunity to personally work with a L67 conversion like yours.

Generally speaking, most all my engine transplant experience has been with the more popular V8 conversions, both OBD1 & OBD2. Generally speaking, engine transplants challenges are, mechanical, wiring, and "Flash". My inexperience with the L67 leads me to think the "Flash" could be the most challenging? Sometimes, wiring can be challenging? The popular LS2 swap wiring can be challenging, but is well documented. Perhaps the L67 swap wiring documentation is not 100% accurate? Generally speaking, the wiring harness requirements for EFI can be simplified to Battery +, Battery -, and Ignition On / Start. The L67 might have wiring / module challenges with the two stage fuel pump system? Without actual experience with the L67, I can only speculate the two stage fuel pump is related to boost vs. non boost fuel pressures? If the engine is only able to run for a few seconds, I can only wonder if the fuel pump working or not? Generally speaking, fuel - air - spark are needed to keep the engine running. I don't recommend using a "Hot Wired" fuel pump, but as a last ditch effort to "figure thing out", hot wiring a fuel pump might be worth trying???

I do not own HP Tuners, so I can't provide input for using HP Tuners with the L67.

dave w