Although the vehicle I am working on is a 2005 Cadillac Escalade, this information is relevant to many OBD2 vehicles. The Tech 2 makes it simple because the tool does not have it’s own battery supply. therefore if the scan tool will not power up there is a basic problem with power or ground to the DLC. Many scan tools now have their own battery supply. When this condition is encountered you generally end up at a screen that states that the module will not communicate. Not a big deal if you know your tool and realize you need to check those circuits. Unfortunately many times a technician is thrown off by this and starts looking for problems with the data communication lines. Yes, I have had this happen to me as well. Once you learn the lesson the hard way, you don’t forget.
As I stated earlier this particular vehicle is a 2005 Cadillac Escalade, but this relates to Cadillac, Chevrolet and GMC full sized Trucks and SUVs between 2003 and 2007 Classic series. So if you have an Avalanche, Escalade, Silverado, Sierra, Suburban, Tahoe or Yukon this applied to your vehicle as well.
I have done this so many times that I went straight to the blown Lighter fuse in the underhood fuse box.
Yes, the fuse was indeed blown. On the fuse box legend, just to the right of the blown fuse is a fuse location marked CIG LTR, 15A. That is the location of the fuse in the fuse box. If you click on the picture below and enlarge it it is much easier to read. You may also notice that this applies to the H2 Hummer as well.
Now we have power at the scan tool and I can proceed with checking the original customer complaint or hot air from the driver’s side vents. For you future readers it is August in South Carolina. Not a real good time to have 140 degree air blowing at you.