Welcome to JustAnswer, my name is XXXXX XXXXX I'm here to help get your problem resolved. Ask follow up questions, thanks.
Use a digital volt ohm meter (DVOM) to measure voltage at pin 7 of the diagnostic link connector (DLC). (2) If full battery voltage is present a problem in the K data communication line is indicated (normal voltage will run from about 2.0 volts to a maximum of about 10.5 volts). (3) Check for installation of an aftermarket radio. (4) If an aftermarket radio has been installed the radio wiring harness must be modified to prevent the aftermarket radio from applying battery voltage to the K data line. (5) Remove the radio and look at the black 8 pin connector. Pin 3 of the black 8 pin connector is the K data line. Remove pin 3 from the connector and tape it back on the harness in such a manner as to preclude shorting. (6) Replace the radio and check for correct voltage at pin 7 of the diagnostic link connector. (7) If 0 volts is present on Pin 7 of the diagnostic link connector a potential short to ground in the wiring harness or a shorted controller on the K data line is indicated. (8) Disconnect controllers on the K data line one at a time while monitoring DLC pin 7 voltage. (9) If DLC Pin 7 voltage returns to normal after a controller is disconnected an internal short in the controller is indicated.