TCU good or bad?

Posted by mac 108, Jul 27, 2005
Automatic Tranny - 4G63 automatic tranny discussions. Sponsored by Import Performance Transmissions

  1. mac 108

    mac 108 Proven Member

    Classifieds Rating:
    100%
    Joined:
    Feb 15, 2005
    Posts:
    108
    Likes Received:
    0
    Memphis, Tennessee
    Ok here's the deal. I have a 91 Mitsu Eclipse GS-T auto with a 14b. I have 3 major problems right now, but I'll address the trans one here.

    I took my car to the local Mitsu dealer (bunch of dishonest crooks) for diagnostics. They say the trans computer is out. Well the trans is in limp mode sometimes and shifts perfectly other times. It comes and goes. I never thought that a computer could work sometimes and not other times. I figured if it was broken, it would never work again. Is it really my computer that is damaged? I pulled it, and it didn't appear damaged just from a visual inspection, but that doesn't tell me much.

    I am suspicious because they also said the IAC was broken and was responsible for my car dying at idle. I replaced it with a brand new one and problem persisted. Spent $300 for nothing (100 for diag, 200 for IAC). Someone please help me out.
    #1
  2. mac 108

    mac 108 Proven Member

    Classifieds Rating:
    100%
    Joined:
    Feb 15, 2005
    Posts:
    108
    Likes Received:
    0
    Memphis, Tennessee
    bump
    #2
  3. 95 'clipse RS

    95 'clipse RS Proven Member

    DSM Profiles:
    1
    Joined:
    Nov 2, 2004
    Posts:
    309
    Likes Received:
    3
    E-Town, Kentucky
    jus to letcha know, bumping can get threads closed, so i wouldn't do that too much.

    anyways, the TCU could be intermittent (working some and not other times), but the only way to know for sure is to have it checked. if they are crooks, find another dealer, or a shop who has the equipment to check the TCU. and you did take apart the TCU and check for leaking capacitors right?? if not check that out, but be careful tho, the electronics are static sensitive. and as for the IAC, that sounds like a steep price OMG you could have cleaned it with gumout, then if it was still bad then replace cuz mostly they jus need cleaning to get carbon and other filth off of them.

    but just have the TCU tested by someone trustworthy, i know thats somewhat hard to find, but thats the only way i see of finding out for sure...

    :dsm:
    #3
  4. mac 108

    mac 108 Proven Member

    Classifieds Rating:
    100%
    Joined:
    Feb 15, 2005
    Posts:
    108
    Likes Received:
    0
    Memphis, Tennessee
    I waited over a week to bump it, if I hadn't you would have never have seen it. ;)

    Anyway, i did open it up, everything looked normal, but I am not familar with leaking capacitors. What do I need to look for? The mitsu dealership here in town is the only one now, i suppose i could take it to another shop, but I will just have to see what works out.

    Haha you'd expect your dealership to get you all the information you need, but sadly that's not the case.
    #4
  5. 95 'clipse RS

    95 'clipse RS Proven Member

    DSM Profiles:
    1
    Joined:
    Nov 2, 2004
    Posts:
    309
    Likes Received:
    3
    E-Town, Kentucky
    yeah i know what ya mean about dealers LOL. i have to drive up into ohio now cuz the one where i live went outta buisness or somethin. to tell ya the truth, the people ive talked to there don't know much about these cars or somethin... well at least at this one...

    but anyways, leaking caps look just like the pc board is wet, cept its thicker than, lets say water, and some areas when it drys has a whiteish, powdery look to it. if not then it should be good...

    to me with the way it sounds to be intermittent all the time, i think that there is a loose connection somewhere in the wiring, check all tranny wiring that runs to the ECU. jus take of the wire wrap around the wires and make sure nothing is snapped first, which is usually unlikely... next check if both of the solenoid connectors are fine, checking the wiring to the pins inside of both of the connectors (solenoid connectors and ECU/TCU connectors) and the pins in the sensors on the tranny. there are two of these sensors on your tranny i think. and make sure that nothing is shorted out to each other also.

    and another thing, have you had the solenoid connectors off at all?? ive heard of some people putting them on wrong because they are interchangable, and that puts some people in limp mode. basically make sure you have clean, solid connections everywhere as to know that the wiring isn't the problem. also, varify that the solenoid sensors are good and working and im sure you'll find the problem somewhere.

    peace
    :dsm:
    #5
  6. steve

    steve DSM Wiseman

    Classifieds Rating:
    100%
    DSM Profiles:
    1
    Joined:
    Feb 3, 2002
    Posts:
    11,753
    Likes Received:
    144
    St. Charles, Illinois
    It doesn't matter how long you wait, it's not allowed.

    Both the ECU and TCU can suffer from capacitor leakage since they both use the same bad capacitors. The ones with EPROMs also share the same type gate array for interfacing the EPROM that seems to go bad.

    Diagnosing the problem for either requires you to pull the computer and check for signs of leakage and repair any damage it might have caused.

    Just because you have a new ISC doesn't mean the old one didn't blow the drivers on the ECU so that it can't run the good one. About a quarter or more of the ECUs I see have blown drivers from either the ISC shorting or from the C106 capacitor leaking and shorting the circuit trace for the ISC that runs under it to +12v.

    Steve
    #6

Share This Page