Why doesn't my Ford OBD 1 digital code reader work?

I have a 93 ford taurus 3.8L V6 automatic GL. I bought a "ford OBD 1 digital code reader" made by Equus off the internet and I am learning how to use it. The model number is 3145. I bought it brand new. I have performed the "KOEO" test with no problem but when I try the "KOER" test the code reader gives me problems. First I warm the engine up. Next I plug in the code reader and cut it on. Then I press the test/hold button. It then shows a "6" which stands for the "cylinder identification code." The book says it is suppose to do this but after that instead of testing anything it just shuts off. The code reader cuts itself off. I can't understand why it is doing this to me. What is going wrong?