A 1995, the European side of Lexus (now Lexus) LS400 sedan, vehicle remote control function failure, the driver side of the main electric glass lift switch can not control the other three doors of the glass lift; with the key to open the door, the vehicle alarm, the engine Can not start; vehicle seat memory function and steering wheel automatic expansion function failure; with the key lock car, the vehicle can not lock; left front door door lights do not shine.
    If the vehicle's doors, luggage compartment and engine compartment cover are opened, the vehicle will alarm and start the engine anti-theft system to prevent the vehicle from being forced to start. If the vehicle is equipped with a vehicle anti-theft system, The As the car can not be achieved with the key lock lock function, we decided to check the vehicle left front door control switch and door computer.
    First remove the left front door of the guard, with a multimeter to check the left front door door key switch. It is confirmed that the switch can be turned on at LOCK and UNLOCK, and the measured resistance value is within the normal range. Then we checked the left front door computer power supply lines, and focus on checking the power supply of the ground line is open or virtual connection phenomenon. According to the maintenance manual requirements, the relevant line of the standard value as shown in the table.
    After inspection, D615-GROUND voltage is not normal, the voltage is about 9V. A fuse (SEC-HORN) is supplied to the terminal. Measured from the fuse to the door control computer wire resistance, measured value of about 800Ω. Under normal circumstances, the resistance of this wire should be less than 1Ω. Analyze the circuit diagram again and find that there is a connector (IF1) in the middle of the wire that is connected to the fuse. So that the connector to find the inspection and found that the metal terminal has been oxidized. After making the necessary cleaning, we replace all the oxidized metal terminals. After the system will be restored and found that the key can control the door lock to open and close, but still can not use the remote control to unlock and lock, while the front door door lights do not light. In the easy repair from the easy to the principle, we first check the door of the light bulb is damaged, after confirming the normal light bulb, but the lamp holder metal terminal exposed to the outside. Check the voltage between the red lead and the GROUND of the power supply and measure it to 0V (standard value 12 to 14V). After analyzing the circuit diagram, it was found that the line was the same as the connector that had just been found oxidized. And then disconnect the connector again to measure the connector to the lamp line is turned on, the measured resistance is less than 1Ω. And then from the other end of the connector to the fuse (DOME-FR) is between the conduction, the result is not conductive. Then check the line from the connector (IF1) to the fuse (DOME-FR) and found that one has been disconnected and found that the fuse (DOME-FR) has been blown. So the wire wrapped in the fuse on the fuse, open the wire to repair, and once again the line recovery, the results of the door lighting is still not bright. And then check the other end of the lamp to the door control computer wire connection, the results line normal.
   And later decided to check the computer, after opening the computer's shell, smell the burning of the circuit board burning paste. Careful inspection found that the circuit board connector below the scorched traces, so replace the door control computer. After the replacement of the computer, the car's various functions back to normal.
    After the accident of the car was carefully analyzed, because the door lights and remote control anti-theft system common use of a fuse (DOME-FR), when the door lights of the two short-circuit fuse fuse fuse, the mechanic did not follow Require the installation of the same fuse, which will blow from the fuse to the fuse between the IF1 (estimated to have been worn before only a small number of several copper wire connection, can barely to the lamp power supply, when the circuit current increases, It will be worn by the root of the wire burning section, while the door control computer internal circuit board because the current is too large and burned). So that the remote control of the receiving system power supply has lost power supply, if the remote control set anti-theft if the above situation, the vehicle's remote control will fail, can not lift the anti-theft. When the user can not use the remote control to open the door lock, can only use the key to open the door, but because the door power supply line oxidation, coupled with the door control computer burned inside, the door lock can not open the signal through the door to control the computer to the body Control the computer (BODYECU), so that the vehicle to identify the abnormal opening signal, so anti-theft function is turned on.