L67 swap PCM issue

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!

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

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

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

Attachment 14205

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.

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

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?

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.

C2 Pin 23 crank voltage?

See attached schematic.

dave w

I did mention C2-23 in the first post. But that's only hot during cranking and considering that the engine cranks and starts up (C2-24 is hot), i didn't think C2-23 was required. Not knowing what its real purpose is, I didn't want to hard wire it to always on battery power. I suppose I can test it using power from the starter solenoid, just to see if anything changes.

According to the schematics I posted:

C2-23 is Hot Only when the engine is Cranking. Connecting to the "S" terminal of the starter solenoid is a good plan, an even better plan would be install an inline 10 amp fuse.

C1-20 is Hot all the time. (Battery +) 15 amp fuse

C2-24 is Hot when the engine is cranking and running. (Ignition Switch On & Start) 10 amp fuse

C1-19 is Hot when the engine is cranking and running. (Ignition Switch On & Start) 10 amp fuse

The injectors and ignition module also need - Hot when the engine is cranking and running. (Ignition Switch On & Start) 15 amp fuse for each one.

dave w

I do have some 3800 Series II experience so maybe I can help. Flashing a 2004 bin file to a 1998 PCM won't work. There is some interchangeability between PCM's, but not in that case. Your tuning software shouldn't have let you write the bin file at all, it should have have some internal tables of what PCM model numbers and what bin file OSID numbers are compatible and prevented you from creating a brick.

I am assuming that when you did the swap you used an L67 harness. What year/make/model did it come from?

The reason I ask is that PCM pin assignments changed over the years. For example, 1996-1997 PCM's are totally different internally, but are pin for pin compatible. A 1998 PCM will physically plug into a 1996-1997 car, but the PCM connectors have to be completely rewired for it to work because the pin assignments are different on the 1998 PCM. On top of all that a 1998 PCM and wiring harness would use a drive by cable throttle body, and a 2004 PCM and harness would be a drive by wire throttle body. The PCM, harness, and all other components on the engine have to be compatible.

Quote:

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Originally Posted by dave w

According to the schematics I posted:

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I have confirmed that all of these are properly hooked up, except for C2-23 which I have not yet tested

Quote:

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Originally Posted by scubasteve231

I do have some 3800 Series II experience so maybe I can help. Flashing a 2004 bin file to a 1998 PCM won't work. There is some interchangeability between PCM's, but not in that case. Your tuning software shouldn't have let you write the bin file at all, it should have have some internal tables of what PCM model numbers and what bin file OSID numbers are compatible and prevented you from creating a brick.

I am assuming that when you did the swap you used an L67 harness. What year/make/model did it come from?

The reason I ask is that PCM pin assignments changed over the years. For example, 1996-1997 PCM's are totally different internally, but are pin for pin compatible. A 1998 PCM will physically plug into a 1996-1997 car, but the PCM connectors have to be completely rewired for it to work because the pin assignments are different on the 1998 PCM. On top of all that a 1998 PCM and wiring harness would use a drive by cable throttle body, and a 2004 PCM and harness would be a drive by wire throttle body. The PCM, harness, and all other components on the engine have to be compatible.

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I am using a wiring harness from a 1998 Lumina LTZ. It is not an L67, all but 2 or 3 of the harness connectors are in the right place, making it the easiest to use and requiring the least amount of modifications. The C100 firewall connector was the only thing that really needed to be altered, and I am confident that I have all of those pins moved to the correct locations.

I have mapped out all 160 pins for the PCM on both cars, based on Mitchell's wiring diagrams. There are of course pins that are populated on one side and empty on the other, but all pins that are present on both ends are the same. The names for each pin does sometimes differ in the chart but I have verified in the diagrams that the wires still lead to the same place. One difference I noted that I don't think matters, the Impala PCM has separate ground pins for a few sensors, for example C1-10 is a MAP sensor ground, whereas the Lumina harness has all of those sensors grounded through C1-17. I would like to cross-check this chart with the factory service manuals, although I don't have a 04 Impala manual. I do have the 98 Lumina/Monte factory manual.

https://s3.amazonaws.com/Quaraxkad/C...comparison.jpg

Do you see anything here that's missing in my Lumina harness, that would prevent the car from running on the Impala PCM but run just fine on a 98 Lumina and 00 GTP PCM?

Quote:

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Originally Posted by Quaraxkad

Do you see anything here that's missing in my Lumina harness, that would prevent the car from running on the Impala PCM but run just fine on a 98 Lumina and 00 GTP PCM?

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I compared the pin assignments, and the things that stick out to me aren't any differen't than what you've already said. C2 19 on the 2004 is an oil pressure switch input and not present on the 1998. I don't know if that is required for the engine to stay running, but it sounds like it won't even start in the first place.

One thing to consider is the MAP sensor. An L67 PCM expects to see a 2 bar MAP sensor. An L36 PCM expects to see a 1 bar MAP sensor. I once put an L67 PCM into an L36 car without changing the MAP sensor. I had purchased a 2 bar MAP sensor but I just forgot to swap it in. It would not start. Once I removed the 1 bar MAP sensor and replaced it with the 2 bar, it started right up.

It's possible that your tuning software never actually disabled VATS in your 2004 PCM. I know when I've done it, several values had to be changed and it was not intuitive at all, but I'm not familiar with the software you are using.

Quote:

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Originally Posted by scubasteve231

but it sounds like it won't even start in the first place.

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It will start and run for a coupe of seconds on the 04 Impala PCM. It will start, run, and drive on both the 98 Lumina LTZ and 00 Grand Prix GTP PCM. Unfortunately I need the Impala PCM due to the transmission incompatibility.

Quote:

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Originally Posted by scubasteve231

One thing to consider is the MAP sensor. An L67 PCM expects to see a 2 bar MAP sensor. An L36 PCM expects to see a 1 bar MAP sensor. I once put an L67 PCM into an L36 car without changing the MAP sensor. I had purchased a 2 bar MAP sensor but I just forgot to swap it in. It would not start. Once I removed the 1 bar MAP sensor and replaced it with the 2 bar, it started right up.

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I am using the MAP sensor that came on the engine, 12580698, google search suggests it is in fact 2bar.

Quote:

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Originally Posted by scubasteve231

It's possible that your tuning software never actually disabled VATS in your 2004 PCM. I know when I've done it, several values had to be changed and it was not intuitive at all, but I'm not familiar with the software you are using.

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That's very possible. However if that's the case, then both TunerCAT and TinyTuner are incapable of disabling VATS. I have tried both. Are you able to download the 2004 Impala SS Stock.cal attached to my first post and disable VATS in whatever software you use?

EDIT: I forgot to mention, I did try hooking up C2-23 to a hot-on-crank source, and that had no effect.

When you are flashing it do you have a separate switched ignition to the ecu so it has both solid 12v and switched 12v because you need to key off the ignition power while retaining the constant 12v feeds for the tune to stay flashed or it will revert to the old vin number and old vats on tune

Quote:

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Originally Posted by delcowizzid

When you are flashing it do you have a separate switched ignition to the ecu so it has both solid 12v and switched 12v because you need to key off the ignition power while retaining the constant 12v feeds for the tune to stay flashed or it will revert to the old vin number and old vats on tune

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Oh... no... I don't have that! I'm using a bench harness, I had no idea that was a requirement! That explains the VIN number resetting itself. However, when I read back the program and check it in TunerCATs, it still has the same settings I chose for VATS so it *seems* like that setting is being saved properly. I will definitely modify my harness now though. How long does it need constant power to stay on after switching off ignition power?

OK, I've done that. Reflashed the PCM and wrote a new VIN. Disconnected only ignition power and let it sit for a minute or two. Unplugged it completely. Plugged it back in, and read the VIN. This time it *didn't* reset the VIN back to default, which is good! So I went out to the car to try starting it up and the battery is dead from all of yesterdays cranking attempts. I've got it on the charger so I'll be able to try again later today or tonight.

EFI Live ... Bench Harness Tutorial .pdf is attached below.

dave w

Went through another entire cycle of changing all VATS values, flashing the PCM, disconnecting ignition power before main power about a minute later. Still nothing. Same behavior regardless of VATS settings. Just to confirm for myself, for the 10th+ time, I plugged in the 2000 GTP PCM, engine starts right up and just runs.

I'm lost.

It appears the 2004 Impala PCM is not supported by TunerCats OBD2.

See attached screen shot below.

My initial thinking of using the 2004 PCM was incorrect, my most humble apologies. :doh:

dave w

It is supported. It's OBD2_28. 2004 Chevy 3.8.

I noticed the OBD2_28 VDF, but seems odd to me to include both NA 3.8 and SC 3.8 with the same VDF. There is a note with OBD2_28, that the Pontiac SC is not supported. GM typically used a different PCM part number for SC vs. NA engine applications.

Perhaps an email to TunerCats would help with the VATS?

dave w

Will your software let you open and write a standard .bin file to the PCM?

I used the GM TIS website, along with a random VIN for a 2004 Impala with an L67, to figure out which OSID's are intended for your computer. With that I was able to find a BIN file that has been mapped.

I'm posting the stock bin file as I found it, plus two versions where I've used the methods I know to disable VATS.

v1.0a is the one I think will work:
-VTD present on car set to 0
-P1626 fault type set to no reporting
-P1629 fault type set to no reporting
-P1630 fault type set to no reporting
-P1631 fault type set to no reporting

v1.0b is a second try if the first doesn't work:
-VTD present on car set to 1 (stock value)
-P1626 fault type set to no reporting
-P1629 fault type set to no reporting
-P1630 fault type set to no reporting
-P1631 fault type set to no reporting

IT RUNS!!

12588500v1.0a.bin was the ticket, thank you so much!! I don't know if it's the updated program version or that my software doesn't disable VATS correctly, but it's running! As an experiment, I took the stock bin, loaded it in TunerCATS and made the same changes you listed here. Then compared it bit-by-bit in a hex editor with your 1.0a bin, and there are three different bits. At position #710CB in my version is #99, in yours it's #9A; and at #7D1C6 my version is #01#FF and yours is #02#00. If I feel like experimenting further, I'll try flashing my version and see if the car stills runs. If it *does* then I'll know that the issue was with the version of the bin I was using as a starting point; if it *doesn't* then obviously my software can't handle VATS on this PCM.

In any case, thank you!

Quote:

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Originally Posted by Quaraxkad

IT RUNS!!

12588500v1.0a.bin was the ticket, thank you so much!! I don't know if it's the updated program version or that my software doesn't disable VATS correctly, but it's running! As an experiment, I took the stock bin, loaded it in TunerCATS and made the same changes you listed here. Then compared it bit-by-bit in a hex editor with your 1.0a bin, and there are three different bits. At position #710CB in my version is #99, in yours it's #9A; and at #7D1C6 my version is #01#FF and yours is #02#00. If I feel like experimenting further, I'll try flashing my version and see if the car stills runs. If it *does* then I'll know that the issue was with the version of the bin I was using as a starting point; if it *doesn't* then obviously my software can't handle VATS on this PCM.

In any case, thank you!

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Excellent! Glad I could help.

Since you have a method for writing bin files to the PCM, I'd recommend using the V1.0a file as the base tune and then use TinyTuner to edit it for any further adjustments. I've had very good results using TinyTuner, and it won't allow you to open or edit a BIN file that it doesn't fully support.