L67 swap PCM issue

[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

[Quaraxkad]

You're absolutely right, the wiring documentation is virtually non-existent for this swap. However I'm pretty sure I have the wiring done properly, considering both the stock 98 LTZ and 00 GTP PCM's will start and run the car. That's what leads me to be believe it's a PCM issue. Regarding the two-speed fuel pump, the way that works as I understand it, is a second output from the PCM switches on and off a resistor in the relay that reduces voltage to the pump. My car does not have that special relay+resistor, just a regular 4-post relay. So regardless of whether the PCM is asking for low or high speed, the pump is always getting full power. Although looking at the Mitchell diagrams I don't see that resistor, so maybe I'm wrong about how it works (or Mitchell is)... In any case, I did try with a jumper wire in place of the relay to run the pump hard-wired, and that made no difference and still had a single cylinder fire and then nothing. That was before I discovered the additional C2-24 power wire though. I will test that and report back. If adding that power wire *and* hard wiring the fuel pump allows the car to run, does that suggest a VATS issue?

[Quaraxkad]

OK, I've just flashed the newly un-bricked LS PCM to the stock SS program, except VATS set to 0 instead of the default of 1. Without power to C1-24, it cranks, fires one cylinder, and then just endless cranking. I can get another single-cylinder fire only by turning the key to off before cranking again. With power to C1-24, I get a DTC as soon as I turn the key to ON, P0452. This is the fuel tank pressure sensor, which my car does not have, so that code is expected. That code being set only when I hook up C1-24 to battery power leads me to believe that it is required to power on this PCM. Although having said that, my bench harness does *not* have power to that pin and I'm still able to connect to it with my OBDLink SX and read/write with WinFlash. So is it required or not?! And now, when cranking it starts up, runs for a few seconds and shuts off. Still sounds like VATS... I also tried hard wiring the fuel pump and have the same result, does this eliminate VATS as the cause or does the 04 Impala do more than cut fuel pump power? I also get two more DTC codes set after that, P0036 and P0449. P0449 is another EVAP code, which is expected. P0036 is an oxygen sensor code, and will require further testing some time in the future. But none of these codes give me any clues regarding the current issue.

As a side note, unrelated to anything else here, I've found that when I change the VIN with WinFlash, the PCM reverts itself back to its original VIN after a power cycle. The VIN doesn't matter for my application, I just thought it was a noteworthy observation.