Compatibility of Early '97 ('96) PCMs

[SSTJ]

Over here, we know that 97 TJs built after July 15, 1996 can be identified by having a ten-digit part number on the powertrain control module (PCM), whereas vehicles built prior to that date have an eight-digit part number on the PCM.

Other than changing the number of digits in the part number, were there other changes to the PCM at this time? I've read that there were software/tuning differences, but I can't get a clear answer on whether there were hardware differences. So, can an early-96 PCM be re-tuned to work in a late-96 "97" TJ, or even in a 98 TJ? (I've read that the 97 and 98 PCMs are usually swappable.)

I've read conflicting information online. I wrote to Mark (WranglerFix) about this, but it isn't something he's explored yet. Also called B&G Performance, but he hadn't heard of this change.

 

[jonny jeep]

The change from 8 to ten digit part numbers shows in the parts lists as before/from July 24th 1997.
I'd have thought that as long as the engine and transmission is the same that they should be directly swappable.
It's possible there may be internal differences but this may have been in preparation for adding cruise control to the PCM which wasn't available in 97 models.

 

[SSTJ]

The change from 8 to ten digit part numbers shows in the parts lists as before/from July 24th 1997.

Interesting. I got it from a Technical Service Bulletin dated September 1996:



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Edit: I see that the Parts catalogue does indeed show a change for July 24, 1997. But that was from seven-digit part numbers to ten-digit part numbers. Now I'm even more confused.

 

[SSTJ]

I checked my 97 TJ, which was built in September of 96. It has the 10-digit PCM. So I think the TSB date must be the correct one, rather than the date in the Parts Catalogue.

I don't know what change the Parts Catalogue is referring to, and why it shows seven-digit numbers (not eight) for the early style.

 

[jonny jeep]

Had another look at the parts list and I was mistaken about it being 8 digits. I just looked at it without zooming in and saw there were 8 digits, obviously I was counting the preceding 0 which isn't needed.
If the parts list isn't accurate it wouldn't surprise me knowing there are mistakes in the FSMs too.

 

[SSTJ]

So far, all I've been able to find are these two differences. Both come from a JTEC Engine Management document.

1) In order for the vehicle to start, both the camshaft and crankshaft position sensor signals must be present. On SBEC PCMs and eight–digit part number JTEC PCMs, both the cam and crankshaft position sensor signals are necessary for continued operation. However, on 10–digit part number PCMs (1997 and later), once the engine is running, the cam sensor signal is not needed for continued operation.

2) Anytime the direct battery is disconnected from the PCM, for approximately 60 seconds, the “Learned Vehicle Configuration” is erased. Erasing fault codes with the DRBIII causes the PCM to perform a battery reset function if the PCM has an 8–digit number. This means that the previously mentioned configuration is erased, as well as all learned memory functions, such as Long Term Adaptive Memory and IAC steps. On 10–digit part numbered PCMs, erasing DTCs clears faults, freeze frames and similar conditions only.