Problem: The owner brought the vehicle in because the MIL was on and the engine was running rough.
Details: The technician installed a scan tool and found a P0300 (multiple cylinder misfire) DTC. With his scanner, he tried to read misfire data and could not. The Tech-Assist consultant advised him to go to Mode 06 (In generic OBDII) and check the misfire count. In Mode 06, he was able to see a high incidence of misfires on all cylinders.
Confirmed Repair: After cleaning grounds F33 and F34, he retested the voltage drops and they were within specifications. He cleared the DTC and road tested the vehicle. The engine ran smooth and the misfire problem was fixed.