Is this possible?

I am sure my ECM on my XJ is failing and I want to swap my '00 ECM & TCM for '98 ECM & TCM. I would use the 98 dash cluster aswell. Anybody see something wrong with this or have some constructive input?

As long as the sensors are the same, specifically the O2, then swapping the PCM and dash should work fine. Same goes for the TCU. You might want to spend some time going over the schematics in the 98 and 00 FSM's to make sure they are the same, with regards to pin-outs on the connectors, sensors, etc.

00 is coil-on-plug, and has a few other differences, but coil-on-plug is the big one.

I went through this when I got a 00 as parts for my 98, and wanted to do the aw4 to nv3550 swap.... I never did it.

fordtech said:

00 is coil-on-plug, and has a few other differences, but coil-on-plug is the big one.

Click to expand...

D'Oh!:doh:
I knew that!

How about simple legality,Id say no,You cant go backwards!

ur right as far as you cant go backwards...atleast thats the way it is here.

what makes you think your ECm is giong bad? also why not just get one from another '00? why do a '98 swap and have to worry about all those things?

also on a side note, doesnt that mess with the odo reading? just curious about that

This is why! Code P1698 - No CCD/J1850 Message From TCM. No CCD/J1850 messages received from the electronic transmission control module (EATX) or the Aisin transmission controller.

I have checked all my sensors and they seem fine. Checked connections at the ECM and TCM no corrosion of any kind. The transmission shifts normally with the CEL on or off.

Also when the CEL comes on the volt guage will peg at 19 volts for a while then drop back to 13.9/14 volts. It does this as long as the CEL is on, never does it when CEL is off. Also if I am not mistaken the ECM controls voltage...?

Most of the information I have researched here and other sources points at the ECM/TCM. I am leaning towards the ECM because the transmission shifts fine reguardless of the situation!

The reason I want to use 98 stuff is because I have a wrecked 98 for parts.

RCP Phx said:

How about simple legality,Id say no,You cant go backwards!

Click to expand...

Thanks for nothing, legality is the least of my concerns right now!! Backwards IS possible, it is a matter of sensors and wiring.

fordtech said:

00 is coil-on-plug, and has a few other differences, but coil-on-plug is the big one.

I went through this when I got a 00 as parts for my 98, and wanted to do the aw4 to nv3550 swap.... I never did it.

Click to expand...

That was the main thing I was concerned about! Coil on plug is the major difference.

first check resistance on the BUS comunication lines between the tcm and ecm. that code refers to a lack of comunication between the tcm and ecm. if there is a high resistance or an open in the bus lines then replacing the ecm and tcm wont fix anything. i'm not sure of the the location of the bus lines in each connector, but they are a twisted pair in the wiring harness. not sure about the voltage issue but i would start by checking resitances.

tribalmentality said:

first check resistance on the BUS comunication lines between the tcm and ecm. that code refers to a lack of comunication between the tcm and ecm. if there is a high resistance or an open in the bus lines then replacing the ecm and tcm wont fix anything. i'm not sure of the the location of the bus lines in each connector, but they are a twisted pair in the wiring harness. not sure about the voltage issue but i would start by checking resitances.

Click to expand...

What would cause the high resistance? I would think a short/ground correct. How much is too high? What would be normal? This stuff is my major weakness, I have always hated electrical wiring.....Damn!! I do know basics to get by though.

any resistance in the bus lines can cause comunication errors. the bus lines cannot be repaired either. if there is a broken line and you solder it back together, you effectively shorten that line and the messages sent between the two wires are no longer in sync. the resistance could be caused by corrosion in the wire caused by chaffed insulation allowing water to get into the wire. it could be shorted directly to ground somewhere, theres quite a few ways it could happen but if the bus lines are the problem you have to buy a whole harness. it's not likely the bus lines are the problem but i'd definately check them before i replaced control modules.

tribalmentality said:

any resistance in the bus lines can cause comunication errors. the bus lines cannot be repaired either. if there is a broken line and you solder it back together, you effectively shorten that line and the messages sent between the two wires are no longer in sync. the resistance could be caused by corrosion in the wire caused by chaffed insulation allowing water to get into the wire. it could be shorted directly to ground somewhere, theres quite a few ways it could happen but if the bus lines are the problem you have to buy a whole harness. it's not likely the bus lines are the problem but i'd definately check them before i replaced control modules.

Click to expand...

Thank you for your input! I will see about checking it though I doubt it is the problem.