Hi,

I've recently aquired a 3.5L TJ Ecu. What I would like to know is if its okay to run this ECU in my 3.0L. I know Harty (AMC WA) runs his 3.0L ECU with his 3.5L engine and has no dramas, so what about the other way around?

i dont think it will work, as the looms will be different
it only works the other way round with the 3.5L engine as your looms are staying in the car hence matching the 3.0L ecu

AFAIK if it will plug in, you will need to have it unlocked (immob removed) by SKR. May be a good opportunity to go for a mail order tune or something.

really? i had a 3.5L ecu and i looked at plugin it in to mine, when i did the conversion, when i compared the 2, the 3.5 ecu had one plug that had more pins on it, plus the BEM thing too

Anyone else with some light on this?

if your going to be installing another ecu into your car you will run into the immob. problem.. you will need to have the immob. removed from the TJ ecu OR go to a mitsu dealer and let them sort it out


as for running the 3litre engine i cant imagine why it wouldnt.. if a 3L ecu can run a 3.5L TJ engine why would it be any different the other way round.. make no sense for it NOT to work...

Ok, from someone who has actually done this

The below is on the assumption you are auto to auto OR manual to manual

3.5 and 3.0 ecu will interchange no worries
3.5 ECU does have the Barra sensor so if you are running the 3.0 harness the check engine light will stay on all the time, does not make any difference to how the engine runs however
Immob, this can be easilly taken care of, you can also run a TJ ECU onto the set up of the TE/F series with no BEM once the immob has been taken care of

If the OP wants more info, plesae feel free to PM me and we can chat


really? i had a 3.5L ecu and i looked at plugin it in to mine, when i did the conversion, when i compared the 2, the 3.5 ecu had one plug that had more pins on it, plus the BEM thing too

Yes, correct, the 3.5 has the solonoid for the Purge Valve and the EGR as well. Will have q pin for the barra as well if was tippy 5 speed will have extra wires for that as well as interface for the tract control. If one car had cruise and one did not there will be extras there also but the actual plugs are identical

Ok, from someone who has actually done this

The below is on the assumption you are auto to auto OR manual to manual

3.5 and 3.0 ecu will interchange no worries
3.5 ECU does have the Barra sensor so if you are running the 3.0 harness the check engine light will stay on all the time, does not make any difference to how the engine runs however
Immob, this can be easilly taken care of, you can also run a TJ ECU onto the set up of the TE/F series with no BEM once the immob has been taken care of

If the OP wants more info, plesae feel free to PM me and we can chat



Yes, correct, the 3.5 has the solonoid for the Purge Valve and the EGR as well. Will have q pin for the barra as well if was tippy 5 speed will have extra wires for that as well as interface for the tract control. If one car had cruise and one did not there will be extras there also but the actual plugs are identical

Just to clear up for myself as this is all new to me (moving on from 2nd gen mode) What is the BEM? What is the Barra? Are they the same thing? Other than that, I have no more questions, thankyou for your help Mal and others

BEM, Body ELectric Module, looks after several things like internal lighting, immob, power window off delay, locking etc etc

Barra, barametric sensor (prob spelt wrong) in short gives the ECU a reading to confirm altitude