96LT1TX

just as the title states, i was wondering if I will run into any unforeseen problems using the OBD1 ECM on an OBD2 car.

I am currently looking at going OBD1 just to use tunercat for the track...it makes me sick to think of paying 450$ for a 10 yr old computer program. At least tuner cat seems to be used more often as well. Any advice on tuning is appreciated, I cant wait to tune myself, and I have been thinking about it for around a year. TIME TO STOP THINKING AND DO IT!

thanks again

shoebox

Probably better posted in the computer/diagnostics/programming forum, but there should be no issues as long as you make the required modifications.

JAKEJR

I just read recently that it can be done easily but there are certain mods needed to the PCM. You might want to check with Bryan at PCMFORLESS.COM on just what's needed.

Jake

Injuneer

You either need to swap out your 96/97 100kOhm knock sensor for the 4.5kOhm sensor that was used in the 93-95 cars, or add a resistor to the PCM pins.

JAKEJR

I thought he was referring to an ECM, such as on the L98, and not a PCM.
Sorry.

So, is that all there is to it?

Jake

Injuneer

"E"CM vs "P"CM has nothing to do with whether the computer is OBD-I or OBD-II. Up until and including the 1993 model year, the purpose of the computer was to control only the "E"ngine. Starting in 94, its was used to control the complete "P"owertain. Not likely anyone would use the old ECM's for an OBD-II->OBD-I conversion, since they are batch-fire injection, speed-density fuel control, and can't control the 4L60E if that's what the drivetrain consists of.

JAKEJR

Right, I understand that.

Where I'm confused is that a PCM which is designed for a OBDII system differs from one that is designed for OBDI in such a way that a OBDI PCM won't work in an OBDII. And in order for a OBDI PCM to be used in a OBDII system, the OBDI PCM has to be re-programmed or modified in some way.

I just came across this topic for the first time a couple of days ago on a different Forum, so I'm just trying to get a handle on it.

I do recall a rather long article in one of the mags recently that identified the differences in the various computers GM has used over the years.

Take me to school on this.

Jake

96LT1TX

Thanks for the info again Injuneer, you seem to be answering all my questions these days
I will look into that knock sensor, that or buy LT1_edit for OBD2, depending on cost.

Eck

I'm running that setup and there is one problem that I have run across:

I cannot get my laptop to successfully read (or write) a tune to the PCM. After countless posts, someone was able to answer why. The wiring in between the PCM and OBDII port are different on OBDI PCM cars that have the OBDII connector inside (like the 94 95 cars).

You won't notice a different if you aren't going to try to mess with your own tuning. However, if you are, you're going to have to mess with the wiring.

From what I've been told, if you get rid of pin 7 on the blue PCM connector, it will clear up the issues (apparently it's causing chatter).

Does that make sense?

Injuneer

The 94 cars do NOT have the OBD-II connector. ONLY the 95's have the OBD-II connector. Yes, the pins on a 95 ALDL connector do not match up in function to the pins on a "real" OBD-II connector.

96LT1TX

so, if I will be tuning with tuner cat, which I will, will I have a problem if I go with the 96 cable, and get my PCMs switched to the OBD1 style? Or will I have to get rid of pin 7 like he is talking about?

these are the kind of issues I am trying to avoid... I am going OBD1 for cost not anything else. So if it will take lots of time to get this figured out its not worth it.

thanks