8g a/t question

hello. i'm having problems with my automatic slipping out of 2nd into 3rd. i was told by my local mechanic that he thought it was a ecu problem. my fluid is not burnt and no cel's. my chiltons manual also states that the shift points are controlled by the ecu. my car used to do this years ago after resetting the ecu via a battery unplug. but it went away after a couple days and i just assumed it just corrected itself. but now after doing a full exhaust and resetting the ecu it is slipping out of 2nd again. is this something i can fix by re-flashing a different stock ROM, assuming my current ROM is corrupt. i should probably do some tuning soon anyway. on top of the full header back exhaust i also want to do the diamante t/b and the outlander intake manifold swap. but all this computer stuff kinda scares me. seems too easy to screw my car. sorry for the long post. any help is greatly appreciated. oh and its a 2002 galant es 2.4

Why not just start with the reseting the ECU? No need to do things if it doesn't need it.

If the problem persists then you know its a mechanical problem not electronic. The next step after the ECU reset (if it doesn't improve) is to perform a transmission fluid flush, using Mitsubishi diamond spiii transmission fluid.

Also all the modifications you list don't require in depth tuning and the ECU should accommodate for any minor changes for mods like you listed.

well i have had the tranny flushed. and i reset the ecu a couple times and gave it a week to relearn everything, even though i know it shouldn't need that much time. do you think it could be a solenoid?

This is a mechanical issue, not PCM related. It is a 2-3 Shift flare that Mitsu has a TSB out for. TSB-05-23-004REVII.

thanks for the info SPD_FRK. so is that a recall or am i gonna get stuck with a bill. i opened up the TSB-05-23-004REVII document and it mentioned warranty and also how much time to charge for repair.

nevermind looks like i need to pay for it.

mine is also doing the same thing, after my full headers back to muffler. hmm... more reason to swap 5spd in. :) summer of course though. :(