[ahhudgins]

Originally Posted by frosty

Thanks for the replies, guys.

So, if I get this correctly, I can either purchase the CodeMate code reader for $39 (http://www.rinda.com/marine/marine.htm#merctool), and read the LED flashes to get the MEFI error code (but not know the exact component that triggered the code),
or spring for the USB -> MEFI cable for $195 (http://www.obd2allinone.com/sc/detai...item=mefiscan1) and use the free software (http://www.tunerpro.net/downloadApp.htm) to read the error codes, and much more.

Am I missing anything?

It doesn't look possible to build your own MEFI cable, must be some circuitry involved.

Thanks for the education!

The codemate is the one I bought and modified. The only thing in a codemate is a switch to put the ECM in service mode and a led with a resitor. I mounted my led in the dash so it functions as a check engine light in the normal mode. The way I read it (I'm going to call and check) the $195 is for the cable and the "monitor" software. It doesn't allow any changes to be made as Jim mentioned. The tunerpro appears to be the full blown software for messing up your ECM so it won't run any more!