I just bought a 2004 GMC Sierra 2500 with 6.0. Took it for a ride and runs great. Driving home and the CEL came on. I came home and hooked my Matco scanner up, can't communicate with the truck. Work car and wifes car work so I doubt the scanner. Checked pins 2 & 5 for voltage and it jumps from 1-3 volts, not 5-7. I still need to double check all fuses and power to grounds but what I'm really looking for is the schematic for the module locations and wiring schematics. I did see some schematics that I printed but they appeared to be for a 1500 5.3. If there is any pointers/advice? I'm pretty confident in my electrical troubleshooting but don't have access to a GM tech 2 or a snap on scanner to see what modules may be an issue. Thanks in advance, Dave