DON'T SHOOOOT ME!!!! This isn't exactly a Third Gen problem, but I always check this site out and i know you guys have the knowledge I need. Here goes... I own a 96 Firebird (V6) and have decided to swap a LT1, complete w/ ECM and tranny from a 93 Bird into her. Everything has plugged/bolted in nicely (and i'd be more than willing to offer anybody help with that aspect of things if I can). However I need some help with the difference in OBD between the two systems. Obviously the 96 is a standard OBD2 and has the appropriate connector... and the 93 ECM is OBD1. I want to make sure I'll be able to read diagnostic/engine codes from the car when everything's put back together. Any information is greatly appreciated.

 

according to lt1swap.com, to do the ODBII port up right, like found originally in the 96-97 Fbodys, the pinout you need is:

Pin 2. - Serial Data - FROM the PCM.
Pin 4 & 5 - GROUND - Usually only pin 5 is needed, however some scan tools/code readers will need GROUND on pin 4 as well.
Pin 16 - 12v+ BATTERY - Power from 12v+ Battery source.
Pin 6 - Diagnostic Request/Field Output Enable
Pin 9 - UART Serial Data
1995 LT1 used an OBD2 port, but were not OBD2 vehicles. These did not have a Serial Data on Pin 2. These used pin 9.


or check it all out here:
LT1swap.com


best of luck finishing up your swap!

 

i would buy and put in an OBDI port and wire it out accordingly. reading OBDI from an OBDII connector requires special cables and makes getting codes a hassle.

 

Thanks for that website.... According to your post & that page, 95 LT1's had the same setup as mine- OBD2 connector w/ OBD1 PCM, so maybe I won't have any problems getting codes from the computer. I guess i'm just worried b/c I swapped mine that way so I wonder if everything will read correctly, but since the relay plugged in right up to my existing wires w/ no problem and i'm using the ECM maybe everything will be ok. I'll find out when I drop the engine back in.

 

@kthxbai- i did some searching & www.canobd2.com sells scanners for both OBD2&1, w/ all the connectors & cables. Of course they're on www.amazon.com for a hell of a lot cheaper than what they want on their site. But i'm not sure how good they are tho.

 

your choice. i was just saying personally i would wire an OBDI port and use the proper scanner.

good luck finishing everything up.

~Steven

 

Hmmm. OBDI and OBD II are completely different systems. There is no way that an ECM programmed for OBDI could be compatable with OBDII. The communication protocols are different and the DTC referrences are so completely different that an OBDII scanner will not even recognize an OBD I controller or visa versa. The unfortunate thing for you is that if you need to be emmissions compliant, and Im assuming you do, your vehicle will have to comply with emmisions standards for the year it was made. This means it will have to be OBDII compliant.

The key difference between OBDII and OBDI are the readiness monitors. Readiness monitors are a series of tests performed by the PCM. Prior to OBDII, vehicles had to be tested for exhaust emmisions to determine compliance with federal standards. OBDII eliminated the need for exhaust testing by programming the PCM to perform this series of very precise tests on each emmisions system several times during each drive cycle.

The fact that the PCM tests itself so rigrously and reports any failure allows the emmisions test center to simply connect a scanner and read readiness monitors and DTCs. If the system's readiness monitors are all complete and there are no DTCs the vehicle passes. OBD II vehicles have as many as 1700 different DTCs to identify different failures. An OBD I vehicle typically had 53 codes.

As far as scanners are concerned. Many generic scanners will read OBD I and II. The Snap On "Brick" is a professional scanner that was the industry standard for many years. These machines are built tough and are easy to use. I keep one in the bottom drawer of my cabinet. As GM is one of the most popular manufacturers, any generic scanner you buy will most likely include the GM 12 pin OBD I interface adapter, along with the global 16 pin OBD II interface. Since Snap On has discontinued the "Brick", which sold new for $2,500, it is now available for about $300 on e-bay or ask your local Snap On dealer.

 

HOTDAMN!!! I'm beginning to think I should just break the car down & sell it for parts... I have to ask some local mechs a few things about this emissions, OBD, and scanner business b/c my heads starting to spin with this overload of info. THANKS.

 

the good news is that with the proper tune you can control that engine with a post 1995 (OBDII) computer and wiring.

what this really comes down to is that to pass emissions since you aren't antique you need a different computer.

its not that big of a setback just think through it.

~Steven

 

well according to some local mechs i don't have to worry about emissions/ smog test b/c apparently virginia doesn't check that stuff- they only look to see if your converter is intact. I'll definitely have to take a step back & "just think through it" b/c i don't want to make it more complicated than it already is

 

I am sorry Roman, I did not mean to throw you for a loop. Steven is right, an OBDII controler will work with your system with the right tune.
Also, If you dont have to worry about emmisions compliance, then this is pretty much a non issue. It may in fact be simpler for you to go with Stevens earlier advise and use a OBDI controller. For data and code gathering purposes, you will need to install it with a OBDI 12 pin DLC. As I stated before, the OBDII communications software will not be compatable with the OBDI program.

 

Remember though, the '93 is a totally different setup than the '94-'95 models. It's an ECM (burn chips) instead of a PCM that came in the '94+ up cars. The dash harness and underhood harness are totally different in the '93 cars so to make everything so it will work like it is supposed to, you need to swap out the dash harness as well.

 

I really appreciate all the advice guys... Between the info i've got here & @ http://www.tacreationsusa.com/3_4_3_8_v6_to_lt1.htm (good site for general info on what's needed to do engine swaps in 4th gens) & like Klortho says, I want everything to work as it's supposed to, so I believe i'm going to swap the dash harness, that'll take care of my OBD issue. I'LL BE ON THE ROAD SOON. I'll post pics in the photo gallery when she's road ready again