OBD II port wont connect

Sound like your code reader has died. If the car was able to be read by your code reader and nothing has changed, and the car still functions good as before, then the reader is bad.

the reader works on another vehicle, gm and everything

Did you have it plugged in all the way ? Was there any codes that needed to be cleared out of the reader before use ? Sorry but you got me stumped.

My 04 has the same problem, did u ever get this resolved?

I'm having trouble with the same issue??? I did install a new head unit but I used an interconnect and everything else is working. Im having brake issues where the peddle goes to the floor and no warning lights!

Replace the AUX or LTR (LIGHTER) FUSE on the EXTERNAL fuse box. IT'S 15 AMP. If it's blown autozone or do it yourself e-checks will not work b.c. no power is going to it. I just went through this an it was the problem. It can also set your check engine light on due to throwing idle off bc it's related to internal ECM input. The fuse box under the hood will say LTR/ ECM OR just LTR. That will be the fuse to check. It's most likely blown if the car runs but you can't get a check engine code reader to pull codes. Because it runs off your cars power through that 15amp fuse. 2006 chevy cobalt LS 2 door.

Who ever posted this fuse-fix is awesome . Why did fuse blow though

I have 2008 SS Had the same problem found out there is a OBD II fuse in one of the two fuse boxes and like the other gentleman said I believe it's attached to either the cigarrette lighter fuse or Like mine was the fuse Box under the hood, I actually had to disassemble it and had two burned out small transistors on the back of the circuit board for the fuse Box and that caused my problem had to replace it with a junkyard fuse Box which if you go the same route make sure you get it out of a 5 speed, because if you have a 5 speed like I do And get a fuse box from an automatic your car won't start. lol sticks dont come with a TCM so the fuse boxs are not interchangeable.

So yes while there is the DLC fuse that shares with the LTR (cigarette lighter/12v Charger) its also common for the pins to become worn and will not make contact when the scan tool is connected. It’s a relatively easy fix to get it to connect by getting the right release tool and new pin connectors. The older the vehicle the more you’ll find the DLC does this. I was having trouble for years until I went to get it smogged. Sacrificed my finger to a pick to bend down the pins enough to make contact. If you have a pin that will go into it from another connector or a broken one you’ve harvested you can do a pull check on it by inserting it into the pins of the DLC if it’s loose it will come out with ease thus need replacing. Good luck and I have done everything to these cobalts and am a GM tech so I know every bit and bolt on these cars.