1990 ECM (Auto vs Manual)

I am attempting to replace the ECM in my auto xj. Is there any difference between the auto and manual ECMs for that year? Looking at the wiring diagrams, it looks like the only possibly shared connection is from one of the TPS connections - which goes to the TCM, but I wanted some comfirmation. Thanks

1990 was non-HO (Renix) setup right? In the Renix setup, there are no connections between the TCM and the ECM. The TPS has dual outputs so each computer gets it's own TPS signal. The diagnostic lines on the TCM go to the big yellow connector on the passenger side instead of the ECM.

If it's an HO engine, then the TPS only has one output going to the ECM, which then relays a copy of the signal to the TCM. There is also a diagnostic connection from the ECM to the TCM. I do not know if the manual ECMs have these connections or not. It's possible the 91-96 ecms have these outputs although I doubt it. I'm pretty sure there are programming differences in the 97+ as TCM codes will trip the check engine light.

I don't know about the 90's but I asked this same question on my '91 and the answer i got was the most obvious diff was pin 29 the guy thought and that this needed to be grounded. I saw this ecm for an auto, but mine is man for 49 bucks! So I was gonna jump on it but when I found that it just don't plug and go I had to rethink it. I guess because the auto ecm has extra sensors say the nss, it may not fit a manual. Hope this helps.

There is a difference. If I remember right from my swap, there is an additional input on the auto ecm that compensates the idle when in gear. The fuel/air curves may be different, but the two computers can be interchanged if necessary.

old_man said:

There is a difference. If I remember right from my swap, there is an additional input on the auto ecm that compensates the idle when in gear. The fuel/air curves may be different, but the two computers can be interchanged if necessary.

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The NSS only tells the TCM what gear you're in and does the starter lockout and backup lites. The only idle related pin on the ECM I know of is the a/c and the extended idle switch (police version)

Oh forgot to mention this. The Renix auto TPS can be used in place of the manual. Plugs right in and you just don't hookup the second connector.