1993 Honda Accord Automatic Transmission Control Unit Circuit Diagram

Hi Folks,

The AT Control Unit on my 1993 Honda Accord has a busted resistor (R41)
in it. Without any kind of printed circuit diagrams, I am unable to
determine what kind of resistor it is. Can anyone help with either a
printed circuit diagram or the resistance value?

Thanks.
Rocky Dada

 

sadly not. unless google quickly spits out the data, suggest a visit to
the junk yard.

if the resistor color codes are still legible, you can read them and buy
another resistor the same value. if they're toasted, the junkyard is
your best bet. regarding wattage, size matters. if the replacement is
the same size, you should be fine.

http://www.honda-tech.com/zerothread?id=962851&uid=999378256&dir=1&postid=11122854

 

ha! if i'd scrolled down...

you'll have to judge the colors for yourself [not sure my monitor is up
to the task]

http://xtronics.com/kits/rcode.htm

1/2 watt, judging by an unburnt neighbor. modern resistors are smaller
for the same wattage than older resistors like this. as long as they're
not too big to fit, use the largest resistors you can for highest wattage.

one thing not clear from that first link is the % tolerance band color
scheme - in this case 5% [gold]. read starting from the end opposite
the % band. also, the value has to make sense based on preferred
values. all resistors use certain values like
http://www.electronics2000.co.uk/data/itemsmr/res_val.htm

if your read value is not on that list, you're reading from the wrong end!

get back if you have any more questions. color pics help a lot.

 

Thanks a lot for the quick response back. Luckily, I had access to
another such unit with the same resistor in good condition. It is
exactly the same as the one to it's left. The resistor is a 15 ohm, 5%
tolerance, 1/2 watt resistor. I plan on getting it from the local
Radio Shack store and work on it tonight. Will let you know how it
goes.

Regards.
Rocky Dada

 

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While you're in there, why not replace some to the capacitors? They're
famous for eventually exploding, and then it's even harder to figure out
what they were unless you find the right web page. You can spot the bad
ones (which have been running HOT) because the plastic label has
regressed, leaving the top of the caps naked.

What wrecked the resistor in the first place?

'Curly'

 

I don't find any other components to be in bad shape but thanks for the
advise.

Rocky Dada

 

yes, but only if they show signs of distress. generally, the quality of
honda componentry is very good, and one of these factors is capacitor
size. in the past when i've replaced them, i've had difficulty sourcing
some of the same types honda uses, and if i do find them, the
replacement has physical size issues.

good question! i believe that resistor is in the output chain, so i'd
definitely check for correct operation of whatever it's supposed to be
driving.

 

Well folks, it did not work out even after replacing the resistor. I
guess I will have to bite the bullet and buy a new (or used) TCU since
I don't see any other obviously distressed components. If it's an IC,
I would definitely not know how to diagnose or fix it. Thanks for all
your help though.

Regards.
Rocky Dada

 

sorry to hear it. to be honest, if a resistor cooks, there's got to be
a reason - and chips are definitely a candidate. make sure your
solenoids are working ok before you discard the tcu.

 

I got into this late, but that is a big 10-4. That resistor was dissipating
several watts (I would guess 5-10 watts, judging by the surroundings) and
that means a short somewhere. A shorted capacitor or power transistor is the
way to bet.

Wrecking yards are the solution, for sure. The circuit board has suffered
more than I like to see, so even finding and replacing the shorted part
would be a partial solution.

Finally - not to worry you too much, but it is worth mentioning - the short
may be external, like the wiring to the transmission. If so, the replacement
will do the same thing. It may be worthwhile to remove the cover of the
replacement TCU so you can shut down power as soon as the resistor smokes
(if it does). Once that is sorted out, replacement of the resistor should
get you working again.

Mike