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ECU-related question

it is my understanding, from what i have read online at various DSM sites, that cars with automatic trannies have both an ECU and a TCU. whereas, manuals have only an ECU.

it is also my understanding that the ECU and TCU do not communicate with each other.

therefore, would there be any problem with using an ECU from an 89 galant SOHC manual for my 89 galant SOHC automatic?

reason i'm asking is because i recently found one in a junk yard for $60, and i thought i'd give it a try. i have yet to completely hook it up, since i need to get a new battery, too, but i thought i would ask the experts before attempting it.

if it doesn't work, my next step is to try to replace the capacitors on my existing ECU. and, if all else fails, i guess i'll be looking for a nice ole' beater car, lol.

the main thing i'm worried about it my car blowing up on me, lol. otherwise, as long as i can get it running for another few months, i'll be a happy man. any suggestions/comments are welcome and greatly appreciated.

-- jshdude

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jshDude
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Hi, My understanding is TCU is likr sub set of ECU which means they're interactive. Like cpu chip vs video card on a PC. They're not 100% independent. Tony

jshDude wrote:

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Tony Hwang

I've seen mention of bad capacitors on Eclipse ECUs on this group. What are the symptoms? Does the ECU die completely, and kill the car, or is the result more subtle?

Dave White

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Dave White

actually, i know that they are independant. the TCU is a separate computer that is specifically designed to control the transmission. the question is whether or not they send each other signals.

i believe the only signals they would send, if any, would be the TCU sending an error code to the ECU. but, i doubt that mitsubishi was that sophisticated in 1989.

-- jshdude

Reply to
jshDude

as far as i can tell, both from word-of-mouth experiences and research, all DSMs in the late-80s to early-90s range have defects with the capacitors on the ECU, in that due to the heat they begin to secret something that corrodes the circuit traces on the board of the ECU, and usually replacing them [given the board is not too seriously damaged] will fix the problem.

the car will crank, but will not start. the shop i took it to for a week tried a new ignition coil, distributor, and spark plugs/wires--all unsuccessful. they eventually told me it was a bad ECU and offered to fix it all for $900. heh. right.

so, after putting all my old stuff back on, and handing the car over to me [after i paid them their "diagnostic fee" of $80], i was able to get it running for a short distance by replacing the battery and finding a used ECU from a junkyard.

as i got around 100 feet from my apartment, the car suddenly died, and i was unable to restart it. crank, crank, crank... but no start. so, my friend and i get to push it to my apartment later tonight after work. fun stuff.

it is very possible that the used ECU i replaced my original one with was bad as well, since they were of the same age. so, my next step will be to order the capacitors and have my girlfriend's father replace them for me, and see if it works.

*crosses fingers*

-- jshdude

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jshDude

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Tony Hwang

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Mike

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