First, my thanks to all the people who make this forum work, take their time to answer questions, and are so friendly and patient. I'm a do-it-yourselfer with a fair amount of experience and this resource has saved me hundreds of dollars. Although I'm unable to donate as much $$ to the forum as I'd like, I do make donations and would like to encourage everyone else who benefits to considering supporting it, also. Now to the problem at hand.

I apologize for the length of my post but feel like one of the reasons I get such good advice here is because I try to give all the necessary info.

The car: 94 Accord 4door EX 4cyl VTEC auto-trans with 245K miles.

I purchased it used with 175K miles on it. History unknown. I use it mostly for highway duty, 40 miles a day at 75mph. No racing or other rough treatment. I do my own maintenance and pay pretty close attention to it. I use Mobil1 5W30, Honda OEM filters, and Honda OEM trans fluid. Engine oil change every 5K, trans oil change every 10K. To my knowledge, it'snever had any transmission or engine work beyond normal maintenance. It's been a great car for me.

When I change the transmission fluid, there's always a thick coating (approx 1/16") of fine charcoal-colored particles on the magnetic drain plug. When I first bought the car, the trans fluid looked a little dark but didn't smell burnt at all. Since then, as I've been changing it every 10K miles, it stays clean and red and smells fine but there's always the coating on the drain plug. Approx 10K miles ago, I installed a large auxillary trans fluid cooler behind the grill (11" x 11" sandwich plate design in line after the radiator-based cooler). There were no symptoms of any kind of trouble at the time; I just thought extra cooling would be a good idea in hot-climate Alabama where I live. Afterwards, I noticed immediately that shifting was more positive.

I drove it to work today approx 20m and noticed nothing unusual until I
exited the interstate. Then, cruising easilyat approx 40mph on city streets it shifted suddenly from 4th gear into 2nd gear. As I drove it on to work, it seemed to shift randomly back and forth from 3rd gear to 2nd gear but was usually in second (when it would normally have been in 3rd or 4th). I drove it gently to lunch (approx 10 miles total) and noticed that it would begin from stop normally and shift normally 1st-2nd-3rd-4th, but then randomly upshift into 2nd (bypassing 3rd entirely). Sometimes it would go back and forth between 2nd and 3rd (or 4th), but mainly it stayed in second. Atthe end of the day I drove it home gently 20 miles onsecondary roads. As I began the drive home, it was behaving normally and accelerated w/o problem up to 65mph; it then shifted abruptly back into 2nd and stayed there as I limped the rest of the way home @ 40mph. This car was designed by Honda to sit in 2nd when it's stopped in gear being held by the brakes (at a traffic signal, for instance), then to shift quickly into 1st as the driver releases the brake and accelerates from stop. By the time I reached home, I noticed that it was reluctant to drop into 1st when pulling away from a stop; it would drop into 1stafter a 1-2 second delay and then shift back into 2nd and stay there.

Miscellaneous info. Whatever gear it happens to be in, it feels normal and responsive and doesn't seem to slip at all except for the normal Honda "slushbox" feeling between gears.It doesn't feel quite as crisp as the trans in alower-mileage Accord, of course, but until today it has performed predictably and as expected (reliable downshifts, upshifts, passing gear, etc.). When I put it in gear, there's an immediate slight jerk, then another one in 2-3 seconds that tells me the trans is engaged and I'm ready to accelerate. The car used to feel like it freewheel-coasted easily in D4 ("like it would roll forever," my wife says) but approx 7K ago I began to feel a slight drag (almost imperceptible) when I released the accelerator at highway speeds. Because the change was almost imperceptible, I ignored it at the time; now, however, I wonder if overdrive had stopped working and it was an early indicator of this looming problem with the upper gears.

As I check through the other posts on this forum returned from a "transmission" search, I get the idea that my symptoms may indicatea faulty transmission control unit. I know engine operating temp will affect the TCU but I use OEM thermostat for this car and operating temp seems normal. Does anybody have any other ideas? Because I do my own maintenance, I tend to try to use high-quality parts (usually OEM) when I can... particularly if the part is hard to replace and labor effort is high; ifthis cardoes need a TCU, does anyone have any advice how hard the job is andwhether I should go OEM vs looking at other sources (ebay, for example)?

Thanks again for your help and your time!

 

I would suggest shorting the service check connector and checking the TCU for codes. Has the D4 trans position indicator flashed at all? There are some codes that don't present flashing D4.

Fine powder on the trans drain plug is normal and no cause for concern. It's fine steel wear from the steel clutche plates. That's why the magnetic plug is there.

You need a Honda shop manual for your model.

good luck

 

I did notice the D4 light blinking at one point within a few miles after I first noticed the problem.

 

Short service check connector under the glove box (blue 2w connector), turn keyswitch to ON, and read flashes. Long flash is 10's digit and short flashes are units (F-ffff is 14). After getting any codes, a reset of the TCU is performed by pulling BackUp fuse (7.5A) in the under hood fuse box for 15 secs. Drive and see if same codes come back.

Post your codes. I have a 94 Accord manual.

regards

 

I shorted the service connector per your instructions and got 5 codes as follows: 13, 15, 1, 8, 9. I let them repeat 3-4 times so I could be sure. I then reset the TCU per your instructions and drove the car approx 10 miles at speeds up to 60mph. It behaved normally for the first half of the drive but then limped home with same behavior outlined in my initial post. Once I got home, I shorted the service connector again and this time received onlycode 15. Both times I checked the codes I also noticed the ABS light blinked repeatedly (not in any long-short pattern that I could tell) but eventually stopped while I was watching the D4-light codes; does that indicate anything to you? Thanks for your help.

 

Code 15 is for mainshaft speed sensor (MSS) fault. It can mean a connector, wiring, or MSS fault. First check the connector and wiring for any obvious faults. The possibility of wiring faults is small, and if nothing obvious I would suggest trying to purchase a new or used MSS (car-part.com). A used part may be difficult to find. Check ebay also.

The MSS harness connector is very near the dual A/B lockup solenoids which are near the trans dipstick. The wires in the MSS harness are Orng/Blu and Wht/Blu. The MSS shows on a graphic as near the trans drain plug on the pax side underneath. Hopefully it is accessible for replacement.

good luck

 

The MSS is likely an input speed to the ABS unit. Once you resolve the MSS fault, this should correct itself. The ABS controller resets w/ every startup.

good luck

 

Do you think the Mainshaft Speed Sensor to which you refer might be the same thing as the Vehicle Speed Sensor? The VSS is located on top of the tranny approx 8" directly below the t-stat. It went out approx 1 year ago with different symptoms (see my posts on this forum and DesertHonda's answers) and I replaced it with a new aftermarket part from an ebay vendor that was much less expensive than OEM list ($20 vs $180). I didn't check codes at the time so have no idea whether code 15 was being generated. The main symptom was that the speedo stopped working; then the unit and connecting wires melted, fuses blew, etc.. Carpart.com doesn't list a Mainshaft Speed Sensor for this car but they do list the Vehicle Speed Sensor for $80. Since I bought it off ebay for $20, perhaps I got myself into a "you get what you pay for" situation and it's gone out again. The connector for the VSS is 3-wire (orange, yellow, black); I just inspected it visually and it looks OK (as far as looks go).

 

VSS is not the same sensor. VSS is Code 4 from the TCU, but also sets ECU code 17.

If you have a high speed internet connection, you can download a 94-97 manual from

http://www.hondahookup.com/manuals/

I've found the electronic is OK, but no substitute for hard copy which allows much quicker acess to information and cross-references.

good luck

 

I repaired the $$ VSS on my 97 Acura TL by replacing the defective pickup coil with a coil from a low cost (accord) VSS I bought. If you pull the MSS, you may find it is very similar to the VSS, and you might be able to do the same. It only requires removing two screws and swapping the topsides to the old body assy. Add grease if the rotating part (magnet) is dry.

good luck