Have an 04 Colorado 5 cyl with a mis fire engine light on

What is your question?

I can not get the code. When I plug in my MAC ET50 code reader I get nothing. Just a blank screen. But I tried my code reader on 3 other vehicles and it works just fine. Is the OBD port controlled by a fuse?

What makes this problem better or worse?

running the engine?

How long has your 2004 Chevrolet Colorado had this problem?

2 days