I built the cable, installed the software, and i get nothing. Will the check light come on while installed into the interface? I'm going back to check the cable. the other com ports say error so i'm sticking with the one that says okay. Is thier a length limit on the cable? any advice?

 

did you use a ressitor across pin a & b

 

i did use the resistor but the light didn't come on. SShould it?

 

No.

 

Don't make the cable too long. Under 10' and you shouldn't have a problem. When you built the circuit, did you build the circuit at the serial port of the computer or at the other end of the cable?
What car or if you know, what ecm are you using.
Double check that the com port is working with some other hardware you might have. A TI graph link for their calculators always helps me diagnose com port issues.

 

Well my first mistake was the cable length. Its about 15 ft. The circuit is at the serial port. But, I'm not sure what i can use to test the port. What is a TI graph?