92 Accord TCU issue; NEED HELP
 

I've got a 92 Accord EX Automatic (154,000 miles) that's having some transmission problems that I think is something electronic.

When my car is started for the first time, it works fine in every way, no matter how long I drive it or how rough I am on it. As soon as I turn it off and turn in back on, the D4 light blinks, and I'm stuck in 3rd gear. I can go to 2nd manually, but not 1st, and the car will shift between 2nd and 3rd gear fine IF I do it manually.

It's been this way for a week or so (I have another vehicle to drive; get's terrible gas mileage), and now it never works.

My thoughts are a bad TCU, but that is only based on research I've done, not on any experience. I'm in college (taking summer classes) and very tight on money, so buy a TCU and trying it isn't the best solution unless I have good reason to believe it's the most likely cause of my problems.

I guess I should say, my thoughts WERE a bad TCU. I pulled it out to look at it, and there were no obviously blow capacitors or burnt resistors. In addition, when I hooked it back up, I thought it'd temporarily clear the problem (again, based only on research), but it did not. I'm also getting the following transmission error codes:

1, 2, 3, 5, 7, 8, and 14


They correspond to:

1-Lock-up solenoid 'A' circuit open or shorted.
2-Lock-up solenoid 'B' circuit open or shorted.
3-Throttle Position Sensor circuit open or shorted.
5-Shift Lever Position Switch circuit shorted.
7-Shift Solenoid 'A' circuit open or shorted.
8-Shift Solenoid 'B' circuit open or shorted.
14-Linear (line pressure control) solenoid open or shorted.


I'm still kind of leaning towards the TCU. It seems strange to me that all of the things malfunctioned at the same time; which tells me it must be something wrong with TCU itself. Also, when I pulled it out, it has "91 Accord Coupe" written on it, so it's obviously been replaced before I owned it. I have had it for 3-4 years, and the transmission has shown no signs of slipping or any other problems before this.

Clear the codes by pulling the 7.5 amp radio/backup fuse in the engine bay fuse box for a minute. Insert the fuse and check for codes (there should be none). When the S light comes back on, check for codes again.

You may want to check for bad grounds. The spooner link I posted in the Online Manuals thread in the DIY section has a 93 shop manual that will help you locate them.

Check for loose pins on the TCU and electrical connectors.

The site car-part.com has listings of junkyard parts that you can search by price or distance. That should help you find a TCU for a decent price.

I found a used TCU for a great price online, and went ahead and jumped on it. It'll take a while to get here, and I'm hoping it'll fix it.

In the meantime, I'm going to take your advice and see where it leads me.

I'll be sure to report back when it's working.

Thanks!

Just put the new TCU in and everything seems to be working. I've been driving the car pretty hard and stop and starting throughout the day to make sure everything seems normal. So far so good, but I won't be satisfied until a couple of days have passed with no problems.

If I don't post again, the car is fixed!