Transmission Control Units

If a Transmission Control Unit is bad, and it's dismantled to look at the circuit board, will there always be a tell-tale burn or resistor/capacitor leakage on the board?

No.

Any idea what on the board would need replaced to make a 'bad' unit 'good'?

Unless you have specialized test equipment to test the TCU, then I can't see any way you could repair it yourself. There is no way to "know" what to replace, even if you are comfortable with repairing PCBs.

Go buy another one from a junkyard.

I did find a TCU at a junkyard for $45. It's something that I don't know about and I love to experiment to learn (thus my love of repairing my accord). I've seen pics of burnt boards and read posts of x-guy replacing a series of resistors and capacitors in the lower right hand side of the PCB, close to the plugs. I've cracked this replacement part and saw nothing on the pcb, neither. I do the transplant tomorrow.

So...guess what? The salvage yard unit is just as bad, actually, WORSE than the one that's being replaced. I opened the case. Resistors in positions 41 & 42 are burnt to a crisp. There're no bands nor coloration left to figure out what the ohmage is. Anyone know what their resistance values are?

You're kidding, of course. The folks here are mighty good mechanics, but they probably don't repair TCUs (even if they could get schematics for them - and I have no idea how you'd pry those loose from Honda).

The TCU is a unit assembled in an electronics factory somewhere. I'd be amazed if Honda makes them themselves.

Play around, by all means. If you can find a hacker site that has all the info you need - sure. But IMHO a junkyard replacement (or several of them) is the way to go. (You're forgetting that not all blown electronic components show any external signs of damage. e.g. semiconductors).

Just wondering if you'd found the values for those resistors. Apparently, this is a common problem. 1993 Honda Accord LX with a damaged R41 and probably R42. Thanks!

R41 & R42 are always the 2 got burnt. But it's not because they are bad, the cause is something else. If you just replace these 2 resistors, it will burn immediately after you connect.

I heard the real cause is a dried capacitor, but I am not very good at these electronics stuff and never got a chance to find out. I have the resistor color code, will post it later. See if you can find out what's really going on.

The 2 resistors are the same. 15 Ohms.