Automatic '90 Accord transmission shifts 2nd and 4th only...
 

I have a 1990 Honda Accord EX with 250,000+ miles (and the car has been in my family as original owners). Over the summer I put in: new spark plugs, new spark plug cables, adjusted the gap on the valves to factory specifications (and compression is to factory spec.), replaced vacuum hoses and new distributor cap and rotor (from the dealer). The EGR valve is good, didn't need replacing.

So, all seemed well until I drove the car about 50 miles, then it decided to pull a fast one on me. When I start from a standstill (in drive), it is in 2nd gear and won't shift out of 2nd with acceleration. I have to manually shift into 4th at higher speeds (say, 45 and up). Same thing with deceleration, I have to manually shift to 2nd. So, the car won't acknowledge that it has a 1st and 3rd gear, nor will it shift between 2nd and 4th. So, it has been sitting in the driveway since summer.

Any thoughts? Some folks say to flush the tranny fluid (which I haven't done for a few years, my bad). Some say that there is a "pan" underneath that could be dirty and needs to be cleaned (but others say that this theory is bull). I could sure use some good advice, hopefully someone out there has had this problem before and was able to solve it effectively.

it sound like the transmission control unit. Its located on the passegers side under the floor carpet. They have some capacitors that go bad in them. I Ordered a new one for my son's 1991 Accord which was doing the same thing but i also just changed the capacitors out and it has been working for over 2 years now. Problem: The usual problem with the Honda Accord transmission, namely the 90,91, -, - Accord, is a bad transmission computer. What happens is that the transmission computer has a couple cheap parts that fail. The failing parts may or may not automatically put the TCU into a saftey (limp) mode (aka, the "fail safe strategy.") The three known failed components are two resistors and a capacitor inside the transmission computer. The symptoms are of several types. The car "S" light or "D4" is on (stuck on no matter what gear selection) or blinking and the transmission won't shift into any gears or sometimes stuck on a certain gear. The trouble codes could be 1,2,7,8,9,15 or None. Shifter interlock control unit buzzes. When the driver steps on the gas the rpm goes high but the car refuses to move at the expected speed. By resetting the TCU, either by the proper method or by disconnecting the negative battery for 5 to 10 seconds will eliminate the problem, but only temporarily. The resistors R41, R42, R43, are overheated or burned and capacitors C27, C28, C32, C33, C5 leaking or shorted. Some resistors will be burned off and we do not know the values. A common sense approach is to consult a working TCU and read the color code on the resistors or start with the highest resistance and go down. Find the best wattage resistor or the best voltage capacitor that can fit. The problem originates with the electrolytic capacitors leaking. Often, the capacitor short circuits frying other components such as your resistor. Another words, the burned resistor is a result of another component failure, namely the capacitor. The fix is to replace the bad parts. See the values below.

Parts values: R41 is most likely 15 Ohms; R42 is 15 Ohms, both appears to look like a 1/4 to 1/2 Watt; Capacitor C28 105`C 220uF 35V Nichicon H9146

Thanks for the detailed analysis Eaglefixer. That may very well be the problem with my car. The "S" (sport shift) light did come on periodically just before this all happened. And the "check engine" light would come on, but less frequently.

When you say you ordered a new one for your son's car, did you mean you ordered just the capacitors, or did you have to replace the entire ECM? I was checking on the computers online and they are a bit pricey.

Thanks again.....

I would check for error codes stored by the ECU and TCU since the check engine light and sport light turned on.

I think that your 1990 accord has the blue two pin connector that you short and you can count the check engine light flashes for the ECU code and the S light flashes for the TCU code. See: http://www.techautorepairs.com/dtc.html

If not, there is an LED on the TCU and ECU that will flash the code.

I did order a overhauled tcu but ended up just changing the capacitors which cost me about $5 which included shipping

I have an 91 automatic accord. it just recently started doing the following: when i put the car in drive and try to accelerate it doesn't seem to want to go...very sluggish. just wandered if it could be the tcu. the speedometer hasn't worked for several years and the "s" light has always flashed when the speedometer stopped working. maybe it flashes due to transmission problems. i recently had an oil change and the service notes indicated a transmission leak which was new. could a leak cause the hesitant acceleration or is it something more serious. the care has about 180, 000miles on it. fearful the transmission may be going out. thanks

Check for engine and transmission codes. See the link I put in my previous post.

Swamplover: The reason for your speedo problems is that the VSS (vehicle speed sensor) has an intermittent problem and occasionally causes the speedo to show zero speed and will also turn on the "S" light...Very easy to fix...holler if you need help.

Same issue
 

Jackson , I am having this issue with my 1990 Cb7 Accord. What should I do ?

Need same help

You are the end of a thread that is over a year old.

So lets try this a bit different. Either post what your car is doing and what you have checked and tested - there are a few in this thread - here. Or start a new one being sure to give the details.....what is the car doing, what you have tested, ect.

There are actually 2 problems discussed in this thread..Which one do you have?

any place where I could the tran comp
??

Honda AT Control Unit Repair
 

HI, I realize this is an older thread. However, The origional response is spot on!
Eaglefixer

My problem is the Capacitors & Resistors. I am in the process of sourceing
these components. I was hoping to get a response from him. One of my Q?
is that he never mentioned the value of the third resistor. Also wether he
or anyone else had ever confirmed the actual value's of the 1st two resistors?

Too bad noone has put together a repair kit containing these 8 parts.

Seems that these are always exactly what's bad. Visibaly anyway mine were.

It looks like one of the posters just copied and pasted the partial contents of this page:
Just looking at the pic on that page shows R41 & R42 marked brown/green/black/gold: 15Ω/5%. You might be able to verify the color codes of the resistors on your printed circuit board if the resistors aren't too burned. This page might help if you find different colors:
You can go 1% on the resistors. Either 1/4W or 1/2W would work, although you can either look at the spec sheet to see if a 1/2W will fit, or just order both since they're so cheap. The electrolytic caps should be clearly marked with capacitance and voltage ratings. You can always go up on the voltage rating as long as the cap still physically fits in the enclosure. Mouser or Dig-Key will have any part you need.

More Info
 

That first site you listed is awsome.

Excellent post. Way to revive an old Thread.

Anyone with this problem should definately consult

techauto(dot)awardspace(dot)com/transmission(dot)html

Also

youtube (search) 91 Honda TCU (look for several posts by) tubejim101.

Both Large resistors appear to be 15ohm. Its hard to tell because most

pics are of burn ones or too blurry to say 100% But All leads point to 15.

I am looking into the smaller

resistor(s). Looks like my R46 & R47 may be Questionable. So I am likely

to replace them as well as R43...

Some fairly decent pic's here:

92 Accord Shifting Problems

cb7tuner(dot)com/vbb/showthread(dot)php?t=169591

R43: BR/BL/OR? 10KΩ
R46: BR/BL/OR? 10KΩ Or RD/BL/OR? 20KΩ
R47: RD/BL/OR? 20KΩ

I really can't tell for sure. You could pull one leg on each and measure them. If they're not completely open then with a DVM you should be able to tell the difference between 10K and 20K or whatever.

Discrepancy
 

Strange.

With a Lighted Tech Mag Visor I can plainly see my colors on the Smaller resistors.

I have the following

R43 Yellow Orange Gold Gold 4.3 Ohm 5%
R46 Yellow Violet Brown Gold 470 Ohm 5%
R47 Brown Black Orange Gold 10K Ohm 5%

Sometimes Brown might look red but compare with other resistors across
the board and I think you will see that Red is much Brighter Red than what
you are seeing on R47 resistor. For example R67 & R68 has red, orange, brown, & violet all close together which helps for comparison of band colors. Use these or some like them to compare and I believe you will come to the same conclusion. As to R46 You are coming up with a completely different combination. Wierd? I am looking right at it and YVBr are my colors.

These are tiny resistors I belive they are 1/4 Watt could be 1/8 even.
But can use higher will not hurt. Fit might be only problem

R 41 & 42 are 15 Ohm at least 1/2 Watt.

I went overkill on my Caps I ordered 50V Caps across the board for all 5 Replacements.

Anyone else chime in on those resistors & Colors... Welcomed'

Lol
 

Just realized you are likely looking at R81 which is Brown Black Orange

Look just above that resistor and just below what appears to be a Voltage Regulator and you should see the actual R43 which is infact

Yellow Orange Gold

I really can't make out the colors. When in doubt, pull a leg and measure the resistance.

Woohoo!
 

I am thrilled to report that my TCU repair was a success! At least so far.

I would like to say Thanks to everone who contributed information on this site and other website posting.

My sport button works again and the car now shifts out correctly!
Drove it around tonight for ~ 30 minutes and everything works perfectly!

I only hooked up the circuit board to the two harnesses & carefully positioned it so that it would not touch any metal.
And only after carfully checking that the board doesn't actually ground via the enclosure(no brads around screw holes).
So I determined it would be safe to try it that way.

I did this so I could observe and quickly disconnect battery at the first sign of a problem. Dont want to let the smoke out!

After parking and cutting it off I delicately felt of the resistors and caps I had replaced thinking they might be hot.
To my suprise NO! They were all cool to the touch immediately after cutting off the vehicle. Which rocks!

Now I feel confident enough to reassemble the board in the box and permiantly reinstall the repair.


Side note to roader... Your last suggestion only works if the resistors aren't bad/burnt!

The values you posted above are incorrect!

Everone should make sure to verify they have the correct information before attempting this repair so that you do not fry your board.


I have posted the correct resistor values in an earlier post above for anyone who cant make out the smaller resistors.

Also I bought 10 of the 4.3ohm R43's but mine did not look to be bad so I did not pull it. Local shops like RadioShack do not carry this value. IF you need one just let me know I will prob never use these. I also have the other two I mentioned. RadioS. did have the 15ohm 1/2 watts.5 for $1.50
Digikey via USPS was the best way to get CAPS... RS had none of them. I went 50v on all caps and although slightly larger they fit well!
Searching for CAPS on digikey can be confusing, lots of choices, If you want my Digikey part# list let me know.

Glad you got it fixed. Two weeks/months/years from now someone will be looking for the same information. It would be nice if this info were available:

• R41 Brown Green Black Gold Gold 15 Ohm 5% ?? Watt
• R42 Brown Green Black Gold Gold 15 Ohm 5% ?? Watt
• R43 Yellow Orange Gold Gold 4.3 Ohm 5% ?? Watt
• R46 Yellow Violet Brown Gold 470 Ohm 5% ?? Watt
• R47 Brown Black Orange Gold 10K Ohm 5% ?? Watt
• C28 220uF 50 Volt 105C (??)
• C??
• C??
• C??
• etc.

Since you have that info, please post it. Also, please include the TCU Honda part number i.e., 28100-PXO-823, in your post.

dejavue
 

I have already posted the correct resistor values for the smaller ones in an earlier post.

My Repaired TCU's Honda part # 28100-PXO-931-M1 3LZ LOT# 9Z05U

As for the CAPS. They are as follows. Note: Even if they dont look bad I'd replace them.

220uf C28
330uf C32
33uf C33
4.7uf C27
1uf C5

I went with 50v on all of them. Fit & Height was not a problem

Might be overkill but the OEM volt ones did not hold up!
And proof is in the pudding. it is working cold to the touch.
Even after driving the vehicle around for some time.

O' and here is my Digikey parts list. This doesn't include three of the resistors I sourced elsewhere.
(RadioShack Resistor assortment pack had 10k & 470's I already had from a previous job + 5pak 15ohm 1/2watt)

4.7uf 493-4506-1-ND $0.70
1.0uf 493-4505-1-ND $0.63
33uf UBT1H330MPD-ND $0.53
220uf 493-13385-ND $1.02
330uf 493-4509-1-ND $1.28
4.3ohm S4.3QCT-ND Qty10 $0.55

They charged 28 cents tax and 2.72 usps first class mail took ~ 2 days.

If you already have soildering equipment - all told this repair costed me about $8 or $9 bucks.

One other thing. The caps I ordered have a longer life / temp rating then the origional.
When i noticed they had different choices I went higher on that spec as well. This info is visible in Digikey's charts.