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1995 Cherokee XJ ECU vs 1995 Grand Cherokee ZJ ECU


Legacy Registered User
the break down, 1985 Scrambler, 1995 Jeep 4.0L/Hesco wiring harness - T5 5 speed transmission, installed YEARS ago. Passed CA Smog Referee with flying colors.

Recently, 2-3 years ago, started to swap in an AW4, its physically installed completely, and runs. Took it CA Smog Referee to see what they think, didn't even come close. The tech says 2 main problems. 1. the AW4 is not shifting into all 4 gears 2. it appears as if the TCU/TCM is not communicating with the ECU. So i started reading. only recently, the last few days I am discovering that while both the Cherokee XJ and the Grand Cherokee ZJ use basically the same engine and transmission in 1995, 4.0+AW4, the XJ uses 2 computers, TCU+ECU, while the Grand Cherokee uses only one, ECU.

So it got me thinking, always bad. What if I am using a Grand Cherokee ECU and adding the Cherokee TCU is only confusing the system. Is it possible to tell the difference physically between a ZJ and XJ ECU, what would I be looking for.

If i were to attempt to build my own wiring harness for 4.0L+AW4 would it be simpler to build for the ZJ single computer set up?

AM I completely insane and seeing something that is just incorrect?



Well-known member
East Wilton
My2C is look for the engine/transmission harness first and build out from there. Lots of XJ's as well that you can utilize. I am using a 95 XJ ECU running an 04 Rubicon engine/manual drive train with a 94 YJ harness. Most of my time was spent looking at the prints and construction differences between years concerning the alternator. Just boiled down to internal vs external diode location. Stayed with the 04 alternator and modded the 94 harness.