I have a 2005 Cadillac STS 3.6l that's giving me a code p0201 and followed by a missfire on cylinder 1. I took it to my mechanic and he stated that I need a new ECM, however, I want to make sure that this is the problem. In other forums I've seen that there could be a short in the wiring or the injector maybe bad and would like to check that first. My question is how do I get to the injector to check it. Where is it located?

So why does he think the ECM (actually, it is a PCM) is bad? Did he do any trouble shooting first before he decided this? P0201 is a problem with the #1 injector and/or injector wiring... this would cause the misfire. You will have one injector for every cylinder. They are located on the top of the engine, in the intake manifold. You probably have a cover over the engine to make it look nice... that obviously needs to be removed. Check the wire that goes to it, especially the connector.

He didn't do any hard core troubleshooting just hooked it up to the computer. And got an "open circuit injector 1". He gave me some print outs as well with readings but I don't have them at the time. Everything else works fine that why I don't think it's the computer. I took the cover off the engine however there's like a big aluminum piece covering must of the top of the engine. Looks kind of like a wishbone.