First of all, the connection diagnosis expert reads the fault code, the fault code displays the CAN communication related fault code, and basically determines that the CAN line is abnormal;
The second step: ready to measure the voltage of the CAN line, so the nearest choice to unplug the nitrogen oxygen sensor, with a multimeter to measure the voltage of the CAN line, CAN high 2V or so, CAN low 1.8V or so, obviously CAN high voltage is wrong, a simple check of the line, did not find the ground worn