The transmission in my TJ Magna has been acting up. I know the transmission was replaced prior to me buying it. Under normal driving conditions it shifts from 3rd to 4th very harshly, but if you floor it, it changes smoothly. I've had it in with my local dealer for a while now, after all the normal checks & about 3 ecu re-sets, it is still the same. At first they recommended a new ecu, but so far that hasn't worked. I've supplied 2 second hand ecu's (as I'd prefer not to have to fork out the $1,500.00 odd dollars for a new one.) Apparently neither of the ecu's I have supplied will even start my car, let alone fix the gear shift problem. It has been suggested to me that I will need to replace the ecu & immobilizer ecu at the same time, with new one's. This is beginning to get expensive & I just want my car back without it costing me an arm & leg. Has anyone out there got any helpful info or know of this issue & how to fix it? Please, I am getting desperate. :eek2:

Welcome to the forum. Why dont you give Mal a call at Mitsfix. His details will be under Madmagna in the forum. He is the wizz and here in Melbourne for you as well. Good Luck.

Tranny Flush with Tranny Cooler Installed.

Approx $250

Great Investment.

SuFz :ninja:

The reason you can't start the car with the new ecu is because the ECU is matched and locked to the BEM module and the immobiliser. A ECU can only be mated to one BEM(BCM) and once it is, it can never be changed or altered. I'm surprised that the dealer does not know this?!

Head to a wreckers like Jolly's in Dandenong or Ringwood, and rip out the ecu and the bem. You must replace both the ECU and the BEM, otherwise the car will not start.

The other part to the system is the immobliser that also needs to be changed. There are a few options for that part:
- Replace the ignition barrel if you can get your hands on the original key for the car you take the ECU & BEM from -then also don't forget the drivers and passenger door handles in that case as well.
- Get the ecu & bem and then have a new set of keys cut by a locksmith and programme that into the ecu.
- Otherwise you can disable the immobiliser (not recommended unless you're getting an aftermarket alarm/immob system of some sort) or program in a new key using a Evoscan cable and changing the ECU settings.

On a side note - to prevent this from potentially reoccurring - have you checked for any signs of coolant on the passenger side carpets? Often the heater core seals can give way and they pour onto the ECU and fry them. The TCU is apart of the ECU module, so if the ecu got doused in coolant then it could very well affect your shifting.

The reason you can't start the car with the new ecu is because the ECU is matched and locked to the BEM module and the immobiliser. A ECU can only be mated to one BEM(BCM) and once it is, it can never be changed or altered. I'm surprised that the dealer does not know this?!

Read ROM from existing ECU, reflash to new ECU - simple fix. or turn bit 3 off in periphery to permanently disable immobiliser.

Immobilser code is hard coded in the ROM.