What does this do

I don't understand why you'd make all this work for yourself. It's not rocket science to deduce failure. At worst it takes the use of a multimeter and a thermometer

 

I can think of one person who would really use this tool and he's looking at making replacement TECU's.

 

According to the book, you can eBay - Page Not Found connect the tester to the car's Thermocouple, using one of the cables provided/made, and read the exhaust temperature (or not if the Thermocouple is bad). You can also compare the left and right temp readings. The Thermocouple which comes with the tester can be used (in place of the existing Thermocouple) if the existing one shows some temp reading but you suspect that it is not correct.

 

I don't know how this Ebay link came in - ignore.

 

I like it.

Where and how did you come about it?

 

Haha. I see one sold just recently on eBay. Hmmmm