OBD1, OBD2, what are the differences?

I've got a '91 XJ and I'm about to yank an engine/trans from a '96 XJ to swap in. I know they are different regarding OBD1 & OBD2, so I guess some sensors will need to be swapped around to make it work, but my main concern is with the flywheel/CPS. Am I going to need to swap the flywheel from the '91 to the '96 engine, or will the flywheel/CPS from the '96 work with my current computer?

Also, what are the major differences in the wiring harnesses between the two systems? Is it feasable to swap mine over to OBD2, or will it be a waste of time? I was just thinking that it would be benificial for diagnostics purposes in the future.


Also, will there be issues with the OBD2 transmission running off of the OBD1 system?

your best bet is to stick with obd I. the obd II trans will probably have fits as well. if you decide to go obd II, grab the entire harness an swap it as well....I would think it would be easier than trying to peice the two together. just my opinion.
edit: to answer the question about the flexplate.....alldata shows them as being the same part #

Stick with the 91 ECM, sensors, and trans computer. The 96 trans will have different connectors on the wiring harness, so you'll have to drop the pan and swap to pull and swap the harness. Use the 91 NSS.

lawsoncl:
My '91 NSS is shot. I haven't taken it apart to clean it out yet, though. Will the '96 NSS work if the plugs are swapped? It seems like it would be easier to splice the old plug in place of the newer one instead of taking it all out of the transmission. But then again, I've never done that, so it may simple to do. Can you provide more detail on that?

four_shot:
Thanks for the info

I'd have to double-check the FSM, but I think the NSS changed connector and an extra wire/contact for telling the TCU when the shifter was in (3). So yeah, you could probably just cut and splice and skip the headache of trying to get them off.

The solenoid harness should be the same, although the colors probably changed. When I swapped a 99 into my 89, I remember the wire colors were very similar (black with stripe versus white with stripe, or something)

If you would do that for me (checking the FSM) I'd greatly appreciate it. I'd much rather adapt what I have than doing the OBD-II harness swap :wow:

Georgia Mike said:

I'd much rather adapt what I have than doing the OBD-II harness swap :wow:

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Good Idea

So it has been a few months, how did this go?

I know someone who rebuilt a '96 OBD 2 engine and installed the long block in a '92. He kept the '92 components on the long block, but failed to swap out the flexplate. He's having fits because it won't start.

I take it the CPS indexes are the same between OBD 1 and OBD 2???

Hypoid said:

I take it the CPS indexes are the same between OBD 1 and OBD 2???

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http://www.chryslerpartsdirect.com/ shows the same driveplate (flex-plate) part number for 1992-2000, so I would assume there is no difference. It does show the YJ flex-plate with a different number in case the donor was from a YJ.

Thanks for the reply!

Both heeps are XJs. He did the sensible thing and used the OBD 1 components from the Jeep they intend to drive. There were some differences in the bracketry. The '96 had more in common with newer models.

I guess I should bone up on OBD 1. LOL Thanks again!