Silverado 3500 4WD V8-6.0L VIN U (2004)
The scan tool will power up with the ignition OFF. Some modules however, will not communicate unless the ignition is ON and the power mode
master (PMM) module sends the appropriate power mode message.
TEST DESCRIPTION
Steps 1 - 4
The number below refers to the step number on the diagnostic table.
4. If the battery positive voltage and ground circuits of the DLC are functioning properly. The malfunction must be due to the scan tool.