my speedometer is working intermittently as well. My o/d light is also flashing and i read somewhere that this was defective transmission speed sensor. does this sensor run the speedometer? How does the speed sensor work, i.e. what is it reading and where is it reading it? Do you have to take the transmission out to get to the transmission sensor? Thanks for your help!

 

Before you replace anything pull the code. Either the cluster or the VSS. probably the VSS. Replacement should be simple.

 

Thank you for your time and response!

The TRANS code (number of blinks of the o/d light) came to 38. I know there isn't a code 38 listed for this car (obd 1, '93 SC40). I've check this a bunch of times and it always links 3 then 8. Strange. The good news is I only have one trans fault code and I see by some pictures they are easily accessible. I think I will disconnect one at a time and check for another code. Disconnecting the good one should throw a new code in addition to the one from the bad sensor. This should point me to the problem sensor. The sensor could be ok and I may have a connector or wiring problem. I'll post the outcome.

 

Turns out I was sold the wrong ECU for my car. it is a 1993 SC400 and requires part number 89661-24230. I bought the right ECU and ALL THE LIGHTS AND CODES ARE GONE = CEL, TRAC OFF, O/D constantly flashing! My car's performance is great - like new!!! It's great to have the correct settings to make your car run the way it should.
My speedometer still has it's problem and it turns out to be the "step motor" that runs it. That is a cheap part, but the labor to pull the cluster off is the issue. However, all my needles have gone dark so I do have to get into that.
I'm just going to enjoy that my car had/has nothing wrong with it - no problem with my IAT/MAF (codes 24 & 31, Nothing wrong with the EGR system (code 71) and no transmission issue O/D code 38, which is a false code from the wrong ECU. Traction control fine (TRAC OFF light).
Its a good day!