OBDII conversion in progress.

[3400-95-Modified]

I only had to splice 3 wires, one power, the tach signal and the ABS signal wire. other than that it plugged right in since it came from the same car that it went into.

I reused all the sensors minus the purge, EGR, and the knock sensor. Other than that they are all the same. At the same time I did however upgrade to the newer pencil injectors. I already had the 3 pin coolant sensor from the 3400 swap.

As far as my dash they are all fed from the sensors themselfs from what I can tell minus the speed, that comes from the ECM. Tach is off the ICM, oil pressure is from the sender, Temp is from the sender, fuel is from a level sensor, and voltage... well yeah thats right there.

[FunkZ]

That's the way the Fbody cluster is as well, speedo is the only one fed from the PCM. So you did not have to convert from single wire OČ sensors to the three wire and add some additional sensors downstream of the cat?

GM used the new style injectors in a 96? I did not think they came out until later. Or do you have a newer engine with the new injectors and the injector wiring harness plugs right up to the older PCM wiring? How are the rest of the sensor connectors between years?

Your PCM is mounted behind the glove box inside the cabin? Mine is out under the hood. That might reduce the need for extra length on some of the wire runs, although who knows due to the engine turned 90°.

[Azrael]

Does your engine harness come through the firewall through that panel next to that summit sticker? Or with that huge bundle of cable coming from the passenger side corner? Your wiring layout looks very similar to mine. I'd find out myself but my car has been in a body shop the past week. I'm much more confident that I can do this swap thanks to this thread.

[3400-95-Modified]

Nope, thats the ABS ECM. There is a Big bundle that goes in on the passenger side to connect to the ECM, and the ABS and fuel pump wires, there is also a Body harness plug in there for the Hvac controls that go out to the engine bay relays.

There is also ANOTHER plug on the drivers side that is where most of the power distribution is located and also the gauge incoming signal wires. If you were to use this harness in a camaro or other vehicle I think you would need to grab BOTH the internal and external harnesses and then merge them together into one so you can get everything right...

Seems like one heck of a project to me though.

I was looking at grabbing a 96 grand am harness once but the body harness plugs on the drivers side differed too much for me to use them, so I had to find a 96 beretta donor. For a Grand AM, I would also suggest getting both harnesses and comparing all the plugs that go between the internal and external harness and you can possibly to what I did and just tweak a few of the wires so it will end up working. I only had to mess with 3 or 4 wires in the engine bay harness to get everything to work with my 95 internal harness... and then obvioulsy I had to add in the OBDII com port inside the car, but thats on my passenger side now to make it easier hooking up the DHP and scanning and such

Need anymore pics let me know.

[3100 MPFI]

I know this is a little late in the game, but has anyone done the OBD2 conversion to an OLDER car?

I am throwing in the hat with trying to get my 1988 Cutlass 3100MPFI to run, and since I have a complete 1996 parts car, I am just going to bite the bullet, and convert it all to OBD2.

Is there anything in particular to watch out for doing a 1996 OBD2 swap to a 1988 Cutlass Supreme?

I already know about 16 wires in the C100 firewall connector are different.

[3400-95-Modified]

if you have a complete 96 then your best bet would be to swap the whole interior harness and the exterior one... That would prevent major wiring diffrences. Luckly my 94 and 95 style beretta's have a OBD1.5 ecm in them so the wiring was very close to identical so I didn't have to change much.

[3100 MPFI]

Interior wiring is completly different. My 1988 is fully loaded, but my 1996 was a base modle.

Besides, I have already hacked up the interior harness to swap some things into my 1995 Cutlass Supreme. I have cut out some of the firewall connector wires, removed the Second gear start switch, cut out the wires for the HUD and DIC, as well as the ABS/automatic headlights.

I also want to keep the 1988 Cutlass Supreme so that it is the flat dash. I mean I have just about everything in that car except for the sunroof (1988 did not get a lot of features, so the best way I can describe the interior is as a fully loaded 1992-1993).

I was thinking about just pulling the IP carrier (I want to felt line all of the contact points anyways to get rid of some of the squeeks and rattles), then re-pinning the firewall connector. That way I can just change out the things that need to be changed, and not have to rewire EVERYTHING. If I use the 1996 dash harness, then that means ALMOST EVERY SINGLE CONNECTOR is going to have to be repinned to use the stock equipment.

[95Grand-Am]

Is there a tech artical or something that I could read, that would tell me what I need and what wires would have to be changed to put an OBD 2 into a 95 Grand Am?

[bszopi]

You basically need the wiring diagrams for your car and the donor vehicle and start piecing together a harness.

[3100 MPFI]

Sorry it's been a while since I did an update. I had a lot go on and had to start over. The original dash harness had some problems, so I went to a junkyard and pulled a complete dash and interior body harness from a 1994 Cutlass Supreme (3100 engine, but flat dash still). That way It would be almost totally OBD2 ready from the start. I have been working on the wiring for almost a month now in my spare time, and I have finally made some progress.

This is a HUGH update covering almost 3 months of work.

Here is the new body harness all taped up nice and neat and ready to be installed.


This is my spare harness from my 1996 Grand Prix. Some of the things that were cut out in the 1994 harness (the one I am using) I removed from the 1996 harness. When I got the 1994 harness, the rear speaker connectors had been cut off, as well as the fuel pump wires. I just swapped out the whole thing. This is what is left:


Here is the old wiring harness coming out of the car.



And this is the first chuck of old wiring I pulled out. I have NO IDEA what it is, and what it is for, or why I even put it in there. It was just balled up under the seat.



This is the new wiring harness getting ready to go in. This is just the PRIMARY body harness with the only things added being the KEYLESS ENTRY.



This is the new harness in place, and starting to put it all back together.









In the new harness, all that I have left to do as well, is solder in the door pin switches, and do some comparisons. I also need to get a connector for the power drivers seat.

FYI, the 1996 floor air duct will NOT fit in a 1988. It is LONGER, and does not line up right.

Check THIS out. I have the provisions for the ABS lines.



This is my current C200 connector. I have the other 2 blades to put in there still. One of them, I have ot make (for the forward light harness), and the other is for the interior lights.



The padding going back in. A few years ago, the interior of my car got flooded. The original padding was not salvageable, so I just got this cheap from Lowes.




This is the carpet FINALLY back in place. I need to get some OXYCLEAN after some of the spots on it.





I also started putting the new brake pedal braket back in.



These are the connectors that are different. Just so you know, I KNOW they are not SPEAKER WIRES.

First of all, In the stock 1988 wiring, there is a 2 wire connector. In the 1994 there is a 4 wire connector. 2 of the wires are the SAME, and 2 are ADDED. I need to know WHAT IS ADDED.



A - GRAY/BLK - DOOR AJAR SWITCH SIGNAL TO CHIME MODULE
B - BLACK - GROUND
C - ORANGE - POWER
D - BLUE/WHITE - DOOR AJAR SWITCH TO CHIME MODULE

My car uses the A, and D wires, but what in there needs the power, and ground.

I also have a 3rd seat belt connector.




The wires are:

A - YELLOW - PASSIVE SEAT RETRACTORS
B - BLACK - GROUND
C - EMPTY
D - EMPTY

I think that the small black connector is for the KEYHOLE LIGHTS, but I kinda need to know what the other connector is for (or what do I need to see if I need to add to my 1988.

Here is 2 weeks of hard work, and pouring over wiring diagrams, talking to people on AIM, etc. I only have 7 things left to do with this harness which all require wiring diagrams I currently do not have, but before I taped this harness up, I first ran the wires for the stuff I am missing so all I have to do is solder 1 wire at each connector.

I am also missing 2 connectors (one for the power trunk release, and one for the center console).

This is the wiring harness that has taken so long to do.



Just so you know, that is spread out and taking up almost half of my queen size bed.

I had taken a lot of spare connectors and as much spare wiring as I could to help me with this. I knew that with having to add HUD, and the DIC, and converting to the C68 climate control that I would need as much as I could get. Here is SOME of the leftover stuff I used in this car.

[IsaacHayes]

So you re-wired the 1994 harness to obdII ? Got a DHP/HPT yet?

[3100 MPFI]

First, I just want it to RUN. The engine that I am using is pretty much stock again. I kept my high lift cam, and LS6 valve springs in it, but it is the stock compression. If it does not run, I will swap in the stock cam (but leave the LS6 valve springs). Once the car is running right, then I am going to restart my performance stuff. I will get the tuner first, but after that, I will start looking into what I want this car to be in the long run. I might rebuild my blown 3100 (my original 3100 MPFI blew up when I drove it 40 miles with no oil in it. I blew out the oil cooler gasket in Houston, and didn't know I had lost my oil until it was too late).

Once the car is even running, I will start doing the performance stuff. That is why I went ahead and put this in the OBD2 tuning secion. I will be tuning it after it runs.

It is actually pretty easy to rewire the 1994 harness to OBD2. The 1994 Cutlass Supreme has the flat dash alread, but also has the 3100, so it is most of the way there. There was only like 5 wires at the C100 connector that I had to mess with. I also had to run the 1 wire for the second data wire (one is the UART DATA, and one is the SERIAL DATA).

Seeing it is after midnight, then TODAY, I am going to go pick up some carpet for the rear speaker deck, and a new parking brake cable, and then I will get back to putting the interior back together.

For now, I am just setting the car up to STOCK settings (basically). This new harness, I went ahead and swapped in the C68 climate control (digital readout) and fixed some things I know I will need later on. Some of the things are just plain easier to do with the wiring out of the car.

I also filled in ALL of the spaces to the C100 connector so that in the future, if I ever need to run anything through the firewall, I can just do it from that connector.

I am making detailed notes of what all I am doing to this harness so in the future, if anyone wants to do this same conversion, it will be easier on them.

I am also thinking about getting a couple of SPARE harnesses and doing the conversion to them, then SELLING them. I know a couple of people that would pay good money for them.

[Hell_raiser]

intresting! good job!

[Shane]

from what i am getting from all of this, correct me if im wrong. but if i wanted to do a 3900 vvt swap the i would need to grab the ecm and all the wiring that comes with it. or would i need other stuff as well?