A 2012 TOYOTA Prado sports utility vehicle with a mileage of about 70 thousand km and a TRJ150L model. User response: when the vehicle is stopped for a second night, it can move away but start stalling immediately. At the same time, the steering lamp and hazard warning lamp do not work. Inspection and analysis: when the maintenance personnel carried out the basic inspection, they found that the car was equipped with a one button starting system outside. GTS is checked by the fault diagnosis instrument. There are multiple fault codes. After storage, only B279A is left. Because the car was modified with one button start, it was considered that there might be a problem with the refitted parts. With the consent of the user, the key start system was removed and the vehicle was restored to its original state. During the demolition process, it was found that there were 2 cauterization lines in the modified one button starting system, but there was no burn mark on the original vehicle line. After the vehicle is restored to its original state, the fault remains unchanged and the fault code is still B279A. Refer to the maintenance manual, it is necessary for B279A to check the data bus of the burglar control unit. To check the anti-theft control unit, we need to disassemble the meter, and the workload is heavy. Because the turning light, the danger warning lamp fault is produced together, in line with from easy to difficult principle, decide first check these 2 lighting faults, see whether there is a connection between the gate and the engine stall. Check turning lights and hazard warning lights with reference to circuit diagrams. Measure the B+ and IG of the steering lamp relay G8. The power supply is normal. When measuring the tie line, it is found that the resistance between G8-7 and G8-8 is 235.5. The signal line of the steering switch and the steering lamp relay is not open or short circuited, but the resistance of the junction point G44-12 and the body is 235.8 ohms, which is also abnormal. Referring to the circuit diagram, it is found that G8-7, G8-8 and G44-12 all pass through the connector J/B NO.3. After checking the circuit diagram of the intelligent boarding system, it was found that the G138-16 of the anti-theft control unit also passed through J/B N O.3, so it was judged that there was something wrong with the connector. Refer to the circuit diagram to determine the J/B NO.3 in the instrument. After dismounting the meter, disconnect the J/B NO.3 and measure the terminals connected to the body inside the J/B NO.3 with the circuit diagram. The resistances are 1237 ohms. Check the connector terminals and find traces of water. The problem is here. Troubleshooting: thoroughly clean the J/B NO.3 inner hole with alcohol, then measure the resistance between the terminals and the body, and change to 0.7 ohms. After the recovery of the instrument test, confirm the troubleshooting.