L7: Check For Short CAN+ to CAN-

At the J1962 connector measure the resistance between pins 6 and 14

- Is the resistance approximately 60 ohms?
Yes
GO to L8 L8: Check For Short CAN+ to Ground
Is the resistance approximately 0 ohms?
Yes
Inspect J1962 for corrosion, bent/pushed back pins or locate and repair the harness. Test the system for normal operation.