Whats involved in replacing the ecu on a 2001 tj magna ? Is it just plug and play or lots of recoding?

Cheers steve

A bit more to it than that, judging from previous posts.

What symptoms do you have from this ECU that make you think it is dead?

Its at the mechanics and there unable to read the puter. There trying to read it due to engine running problems and weird stuff that's been happening. A faulty puter does seem like the candidate. He hasn't put a price on it yet but his words were "ouch"

If a mech or auto elec try to source an ECU it would normally be anywhere from $1000-$2000.

Get yourself one from the wreckers, take the part no off yours and get one with the same numbers then you should have to do nothing. My TE 5 Speed shorted out my ECU, so I found another TE 5 Speed, they had the same model numbers so it was a straight swap. The ECU from the self serve wreckers down here cost about $66 IIRC.

Get yourself some wire, stick in into pin number one on the plug under the dash on the drivers side, then attach it to an appropriate ground, this activates the manual code reading sequence, the engine light flashes a few times slowly then enters a fast flashing sequence, if you can read the codes this way then I wouldnt think the computer is shot.

What is common with these cars, the heater core is located above the ECU, the heater core seals leak and coolant drops onto the ECU which causes a short and a lot of running problems. To diagnose the heater core letting go, pull up the passenger side carpet in the footwell, if the footwell is wet then chances are the heater core is infact leaking and so you need to either replace the seals (which is a "dash out" job), bypass the heater, and then replace the ECU.

You can't just whack a second hand ecu in as it won't start due to the immobiliser. The ecu and bcm are paired units (along with the key). The only way you can get away with just replacing the ecu is to have someone flash it (and disable the immobiliser) but you then lose the immobiliser function.
If you don't want to lose the immobiliser then you'll need to replace ecu, bcm, keys, key barrel and locks. Mitsfix would be able to assist with sourcing these bits, and at a far cheaper rate than your mechanic will charge you.

And, as peaandham noted, check the heater core for leaks as this is generally the cause for ecu failures.

You can't just whack a second hand ecu in as it won't start due to the immobiliser. The ecu and bcm are paired units (along with the key). The only way you can get away with just replacing the ecu is to have someone flash it (and disable the immobiliser) but you then lose the immobiliser function.
If you don't want to lose the immobiliser then you'll need to replace ecu, bcm, keys, key barrel and locks. Mitsfix would be able to assist with sourcing these bits, and at a far cheaper rate than your mechanic will charge you.

Ah right, I didnt note it was a TJ, as the TE/TF doesnt have the same bcm issue.

Thx for all help the guys ....as the mechanic said ouch

Its at the mechanics and there unable to read the puter. There trying to read it due to engine running problems and weird stuff that's been happening. A faulty puter does seem like the candidate. He hasn't put a price on it yet but his words were "ouch"
Note that a common OBD2 scanner won't read a Magna ECU - the scanner must support the MUT protocol to communicate with the ECU. If the ECU is alive and showing faults, the "flashing lights" method for reading fault codes should work. If the engine is running, even if badly, the ECU is not completely dead.

Note that a common OBD2 scanner won't read a Magna ECU - the scanner must support the MUT protocol to communicate with the ECU. If the ECU is alive and showing faults, the "flashing lights" method for reading fault codes should work. If the engine is running, even if badly, the ECU is not completely dead.

Yeah what is the bet the mechanic has the wrong scanner for a Magna (pre 2006 Mitsubishi vehicles (in Australia) don't work with OBDII scanners).

MUTII is what you need and if your area is a lot like mine only Mitsi dealers have them.

There's a place here in Adelaide that can check Mitsu ECUs, walk in service. I suspected my TS ECU was dead, but it turned out it was a blown ignition coil (ECU checking place told me to bring those bits in - coil, distributor - when the ECU showed ok and put them on a test rig). Worth getting those bits checked before you blame it. No point changing the ECU, BEM etc if it is a problem with the coil.

Current question is - is the ECU actually broken, or is the mechanic using the wrong scanner?

PS The paperclip method works, there is a DIY ECU reading thread in the DIY section you could read/print/show to mr mechanic.

Any Snap-on scanner using the S-15 key and DL-16 adapter will be able to communicate with the mits ecu (its what we use)
The Carman Scan will also work (had the rep demo on my car)
and im sure many of the other expensive ($6k+) units will too.... i've yet to hear of a professional workshop using a cheap ebay toy.