Auto Parts: pcm, powertrain control module, noid light

Question
my 03 tahoe is blowing the pcm1 fuse I am not sure where the powertrain control module is to check or change it or if that is even the problem any help would great. Also where would I find one and about what would it cost. Thanks so much for your time.

Answer
    Powertrain control module is GM's jargon for the ECM, the module (or computer) that controls the engine and transmission.  They changed the name when they started using electronically controlled transmissions.  GM mounts these units in the passenger compartment, usually screwed directly to the inside of the firewall in front of where the passenger sits, kind of tucked behind the heater box.  There are several possible faults, and almost all of them will require replacement of the ECM.  You should be able to buy a remanufactured unit for around $150 with exchange of the old one.  It will then have to be reflashed to match the latest programs for the vehicle.  This service can cost about $100-$150, and can be done before you get the unit, so that all you have to do is plug it in and go.  But, I would remove the unit first and check it visually for any obvious problems like water damage or being kicked by an overly enthusiastic passenger (hard to do but not unheard of; water damage from snow or mud on boots is even possible.  Write down all of the numbers on the module before ordering a new one, or take it with you to the parts store.  The PCM (or ECM) controls the injectors by grounding them, so all of the injector current flows through the unit.  If you have access to a noid light, check all of the injectors to see if they are firing correctly.  Of course you can only do this if the fuse isn't blown.  If it blows immediately after key-on following replacement, then the PCM is almost certainly the problem, not an injector or the injector harness (a pinched wire can ground the injector circuit).  If you can get it to run for a little while, you should get a tech with a full bore engine analyzer (not just a code reader) to check it out; if there's a fault, he ought to be able to see it.