seagrits

Hi folks, another newbie and thanks in advance for the help. So, here goes;
93 Accord Wagon Ex. The dreaded blinking D4. Shorted pins out on blue plug behind passenger side kick panel, results 7 short blinks.... or Shift control solenoid valve A. Did a search making sure I was on the right assembly, pulled the plug and found 15.4 ohms to ground on one wire, 12.1 on the other. For grins, checked the other two solenoids (connectors were side by side) and both read 15 ohms to ground. I then pulled a jumper from + on the battery, engine off and fed 12 volts to each of the two solenoids and did hear a distinctive click. So next; I've done some digging under the dashboard in search of the TCU. So far, the only thing I've found that I think may be it is marked CONT AUTO CRU. Made by Jideco pt#ET70-404 DC12V. If this isn't it, where else could it be?!? Secondly would you recommend swapping out the shift control module (two solenoids) since there is 3 ohms difference?
BTW...I did reset the tcu and drove down the block, did fine for the first mile. turned around, got the blinking light and code again and did notice that I went from what seemed 1rst gear to top gear with no in between. Again, many thanks for the help.

v4lu3s

one other thing to try before spending money is take the solenoids off and clean them out SOMETIMES this helps. if not then i would say get a pdf copy of the helm manual and run the diagnostic for the code 7....if it says new tcu good luck! i recall years ago putting in a 94-95 into an earlier accord and it working though it seems it may have thrown a weird code...

seagrits

Thanks v4. I'll plan on this task tomorrow and let you know how I came out. I did find a pdf service manual...genuine honda which states the resistance reading should be from 14 to 16 ohms. Clearly one of the solenoids is a bit out of tolerence. Does two ohms make that much difference? Electrically it would mean the the bad one is pulling two tenths of an amp more to energize. I'm wondering if the tcm has been overloaded a bit because of the "sick solenoid". The more I work on this thing, the more I like points, carburetors and a real pedal engaged clutch!

v4lu3s

lol
that far off could cause a problem, i believe that would cause 6 more amps of current draw to activate the solenoid which could very well be enough to damage the tcu. i would start with replacing the solenoid, used or new as long as its within spec, and then see what happens. if you have to replace the tcu and cannot find another exact replacement see if you can get it from a junkyard and maybe they will let you try a few obd1 tcus to see if one from another year will work ok.

seagrits

The bad one is reading 12.1 ohms. 12 volts / 12.1 ohms= .99 amps. On the good solenoid readings; they are 15.2 ohms using the same formula V/R=A would pull .78 amp. Roughly 2/10ths of an amp less current on the good ones verses the bad one. I'll holler at ya tomorrow and let you know how bad these solenoids are after I pull them. Also will find the tcu. I have found a sight which shows some of the electronic components that have proven to go bad over the years so may be able to do some soldering and throw in a resistor and capacitor or two. Thank again v4. Had an old ford falcon in my youth....200 c.i. inline six, three on the tree and a one barrel carb. Now, that was something I could work on!

crazymikey

Try removing the shift solenoids and cleaning them out. It's I think 2 or 3 10mm bolts on the front of the tranny with 2 round cylinders sticking out of it, staring you right in the face. Clean out the filters and the gasket and put it back.

I had the blinking D4 light, and it was my shift solenoid B, which was causing the car to disengage overdrive. I removed it, cleaned it up and never had an issue again.

As for your TCU location, on all 90-93 Accords, the TCU is located next to the ECU in the passenger side footwell, under the carpet. To tell the difference, your ECU will be the one with a code on it such as PT6.

TCU's occasionally go bad, but clean up the solenoids before you go changing TCU's.

Replacement solenoids can be had at the junkyard, or they're on ebay around $50. It's sounding like one of your solenoids is bad, but maybe a cleaning will help. If not, I'd still replace the solenoid before the TCU.

MAD_MIKE

Check the resistance values of the solenoids when they are both cold and hot.
12-24Ω is the operating range.
http://techauto.awardspace.com/transmission.html

seagrits

Great info fellows, thanks. It's ironic that you say pull the solenoids before the tcu. After an exhausting search the other day on the web, I finally found (before your posts) where the the tcu was...and did the reversal of your recommendations...yea, stupid, right?! I work on cnc machines for a living and electrical / electronic junk is always easier than playing contortionist with wrenches! I did pull the tcu, pulled the board out of the cover and found some crud on it but all the electrolytic caps and associated resistors both looked and checked out electrically fine. I cleaned it all with contact cleaner and a tooth brush..walla, looked like a new board. This morning after a chilly morning deer hunting I put the thing back together and drove down the road....you guessed it, D4 started blinking again. Did the short on the blue plug and back to seven short blinks. So, I'll yank the solenoid pack out today. This is a great forum with good folks on it...thanks again!