vedha

If some one knows about Honda Accord Ex 1990, the faulty circuit board
specs,. At Control Unit 28100-pxo--931-M1 3LZ .
I have replaced capacitors and resistors I need help because resistor keeps burning specially (R88 & R69) 2 ohms each. is there any thing out of box to be looked into? The problem is the shifting of the 1st gear and everything else shifts fine so . help please.
Here is the link for the TCU board. Thanks.
http://techauto.awardspace.com/transmission.html

poorman212

Not sure of the year here.

Are the new parts buring out. Have you check cleaned the solenoids on the trans.

Snozzy

I replaced the burnt cap and resistors on the board for my 1990.... didn't last an hour before the new resistors failed. I also noticed the main chip got very hot as well. I found a replacement TCU on EBay for $20 shipped.

Just wondering, is your TCU made by OKI? My old one was labled as being made by OKI USA, so I looked for another manufacturer. The TCU I got was Japanese made and is totally different from the OKI USA board. The repair writeups I have seen all look like they are working with the OKI.

I've put about 300 miles on the new TCU... works like a charm.

vedha

Yes it is OKI, USA a blue label. when I went to junk yard I found
TCU from Accord LX not Ex, anyway I replaced it, now the 2nd gear is skipping and the green light is flashing.
When ever I replace the resistor on my original board it only last like and hour max and it burns and goes bad a result the 1st gear is skipping and the RPM goes high while the car start moving,
then good to go on a highway until I come to complete stop.

vedha

vedha

I did clean solenoids some time ago and I will recheck it but sure
it is not the problem.

vedha

vedha

I saw there are two solenoid attached up and down behind the radiator the one which is up, I cleaned it and nothing was really there
but the one on the downside I don't no about it, should I have to
open that too, is that is the one you are talking about?

poorman212

The "upper one" should be the lock up solenoid. The lower should be shift control. Yes they both need to be tested/cleaned.
Still not sure if this is causing the issue, there could still be something else in the TCU causing the issue, I think this gen did have issues with the TCU's.....Just hate throwing parts at an issue hoping it fixes the issue.

holmesnmanny

What's the best way to clean them(taking them apart etc.), I've never done this before and it might be good preventive maintenance.

vedha

vedha

Yes I removed both the solenoids, lock up and shift it seems to be
in good condition no black content just ATF in red color. I did it
because I want to eliminate the causes.

vedha

Finally the problem is solved when I noticed that the electrical connector of the
solenoid was corroded by the antifreeze leak. Just above the connector is the
hose going to the radiator and the slow drip of the antifreeze over a period of time
damaged the terminals resulting in the high resistance to the flow of current.

cpwilliams1

I have a 1991 Accord LX that had an (S) light continuously blinking while the transmission would only move in 2nd gear or third gear. It would not begin in 1st while in D4. After reading many threads on the topic I finally opened up the TCU/TCM (Transmission Control Unit or Module) computer to look for damaged components I didn't find anything. Finally I read Vedha's thread regarding the possible antifreeze leak on the engine side of the top radiator hose onto the larger of the two connectors below. Now, I remembered washing my engine a week before I started to have this problem. So I check it out and low and behold, there was green corrosion inside the right connector. I understand that this connector may control shift solenoid. After cleaning it with DW40 and brake cleaner and finally packing the connector with clear silicone grease the problem was fixed. It's now shifting perfectly and the (S) light is not blinking any longer. I am sure you saved me and others the frustration of having to fork up many hours of troubleshooting as well as hundreds of dollars in parts changing. Thanks to all and especially Vedha for your threads.