OBDII swap checklist

[Azrael]

This is what I've been able to cobble together so far. I haven't actually done this swap so I'm hoping some of the knowledgeable people here can fill in the holes and correct any mistakes. I'll do my best to try and add all the useful info anyone cares to add. This is mostly aimed at those wanting to go from OBD1.5 -> OBDII. There might be more or less work required when swapping from an OBDI setup. As for any needed sensors, it's probably best to buy them new rather than to pull them from a junker.

- 1996+ PCM from any vehicle with a similar engine and transmission setup. A 96 PCM is listed since it will work but a 97 is preferred for it's added tunability. It doesn't seem to matter which vehicle it's pulled from as they all use the same pinouts during these years. Some donor vehicles for 3x00/4T60E setups: 96-98 grand ams, 96 (+97-02?) grand prix se's, 96+ luminas, 96+ monte carlos. Probably more including some minivans.

- 96-98 engine wiring harness from a vehicle with the same engine and transmission. It's generally best to get one from the same chassis if at all possible. Otherwise go for one from a W-body (grand prix or monte carlo) as those cars are larger and should provide more wiring length (I could be wrong on this). Also grab the seperate injector harness.

- GM went with a single coolant temp. sensor with the computer upgrade. This might not be a concern for those without a dashboard coolant temp. gauge. Either way it'd be a good idea to get it from the same car as the wiring harness to avoid unneccessay wire splicing if any of the connectors are different. If your car has a seperate signal wire for a coolant gauge then get a 3-pin sensor (AC-Delco part number 213-815) and replace the connector with a spare TPS connector from any 3100/3400. The wire to the gauge needs to be spliced into the 'middle' wire of the connector.

- New knock sensor. Once again it's best to get one from the donor of the wiring harness.

- MAF sensor. This shold come from the same vehicle that the PCM came from unless you're savvy with custom tuning. This is probably the only sensor worth getting from a junkyard as it can be quite expensive to get new.

- ABS system. Both the computer and the pump module on the master cylinder are different.

- Transmission switch. The switch itself functions the same but the signal used by the PCM is reversed. You can either splice in the connector from the old harness or simply just grab the newer switch to avoid wiring complications.

- Evap purge system. GM made a minor alteration by adding an extra solenoid. Grab the whole bracket the solenoids are mounted to under the ignition module.

- EGR valve and connecting pipe to the exhaust manifold. GM went from a digital EGR to a linear one in 96. These can also be grabbed from the donor car of the wiring harness.

- Second O2 sensor + wire to main harness. It's only there to make sure your cat convertor is working so just get an O2 simulator. One less sensor and less welding to worry about.

OK. Everyone feel free to chime in.

[Rhedalert]

you pretty much got it. There are some additional things I had to do:

On my chassis (W) I had to modify the firewall connector wiring a little (connection between interior harness and exterior- "C100"). Power distribution changed in '96 on my car. There were several changes, however it only involved moving 1 wire and modifying another. I don't know if this would be the same for you. I have to dig up my old research and post it here. It might be worthwhile for you to get an N-body harness, since you'd still want to retain your interior harness, and a W-body or other platform will probably have a different interior harness setup.

The EVAP system will set a code, but not the check engine light. The same EVAP purge solenoid is used, but there's one additional purge solenoid (not the same, almost looked like a vacuum controlled unit but it's not) you can see the routing on the emissions sticker. Why they added to an already good setup I don't know.

Don't forget there's also the downstream Oxygen sensor too (after catalyst) I just bought an O2 simulator from http://www.zzperformance.com/grand_p...ts1.php?id=179 (I hate the site but that one product DOES work and is reasonable) just be sure to grab the O2 sensor harness that heads down there.

Also be sure to grab the upper engine/injector harness, as the plug is different where it attaches to the main harness.

The tranny switch is just the connectors, yes. GM did change the type of "signal" going from the switch to the PCM, however the switch functions the same. '95 and older use a ground signal IIRC while '96+ uses a 12v signal. I added the '95 plugs to the OBD2 harness thinking I was going to use that tranny, but ended up buying a '97 trans and just used that particular switch. So I have the plugs I added taped off to the side (I can use either switch) Best to just grab the switch.