A BYD F3 car with a distance of about 13 thousand km. The starter does not work at the P and N position. The cause of the fault is: the anti-theft device is not unlocked; the fault between the anti-theft device and the gear switch, starting relay and so on; the malfunction of the gear switch setting and the starter fault. Fault diagnosis: (1) remove the body anti-theft controller, connect the No. 5 foot (black) directly to the iron, start again, and the starter still does not work. (2) remove the gear switch connector, measure the body anti theft controller No. 5 foot (black) to the gear switch 7 foot (black / red) wire harness, which is good, indicating that the starting relay and the related wiring harness are good. (3) put the transmission rod in the N position and measure the conduction between the 7 foot and the 8 foot on the gear switch. It is found that it is not guided. When the shift lever is gently sloshing, it can be conducted occasionally, indicating that the position of the gear switch is not adjusted. (4) re adjust the gear switch according to the following methods: place the shift lever at N position. 2. Remove the connector on the gear switch, loosen the connecting nut between the cable and the manual switch lever of the gear switch, and remove the shifting cable. 3. Pull the manual control lever, align the end hole of the manual transmission lever and the flange hole of the transmission gear switch, as shown in Figure 1. Note: in order not to move the switch, it is suggested that the transmission gear switch can be inserted through the metal pin of a diameter 5mm to the tip of the hole of the manual transmission lever and the flange hole of the transmission gear switch. (4) installing the shift cable in the corresponding hole of the manual control rod, fastening the gear shift switch assembly nut to the prescribed tightening torque, and stipulating that the tightening torque is (11 + 1) N m. Push the switch switch harness connector into the socket until the wiring harness is tightened. Check whether the gearshift lever is in the empty position. Check whether any position of the manual lever is consistent with the position of the shift lever. Troubleshooting: adjustment after the test, troubleshooting. Maintenance summary: the main function of the AT shift switch is to give the current AT location signal to the combination instrument, give the AT controller signal, make it know the current gear position, control the starting relay power, so that the engine can only start at P or N bit. Attention should be paid to checking and adjusting the parts of automatic transmission in daily maintenance.