data link connector problems, 2005 avalanche,
 

I failed emissions. it said no voltage. they said it could be the cigarette lighter fuse. first I have to explain what led up to this. right before last summer ,the lighter fuse burned out. I replaced the fuse and it burned out again. when I would plug a charger into the other plug it would start to work and the start flickering, and then the battery would die. a quick charge and it was like nothing happened. then the blower stopped working. I changed the resistor, and harness. when I hook the blower up to the battery It works but won't work when hooked up inside. I bought a new switch and it still doesn't work. tough when it's a 115 out. also my speakers on the passenger side stopped working. then, all but the speedometer, and fuel gauge stopped working. so now, I fail emissions and iv'e put new fuses in. the dlc gets voltage, but it won't receive codes. also, the lighter doesn't blow the fuse now. any ideas out there? is it the ecm? thanks.

Welcome to the forum...
Wow sounds like you have some shorted wires somewhere:confused:
Check all of your fuses both under hood and in the passenger compartment...
I believe the data comes from the BCM not the ECM...
attached is the DLC schematic

The data link connector (DLC) is a standardized 16 cavity connector. Connector design and location is dictated by an industry wide standard, and is required to provide the following:

• Scan tool power battery positive voltage at terminal 16

• Scan tool power ground at terminal 4

• Common signal ground at terminal 5