L67 swap PCM issue

[Quaraxkad]

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

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.

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.

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

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.

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.

[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

[Quaraxkad]

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

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?

[Quaraxkad]

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.

[dave w]

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

dave w

[Quaraxkad]

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.

[dave w]

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.

dave w