Failure phenomenon: a 2001 annual Mercedes-Benz S320 sedan, W220 chassis configuration and M112 engines. According to users complained that after the vehicle is parked overnight in the morning the car door by remote control does not respond, after several press the remote control (probably dozens of times), and finally the central locking the doors opened, and after a long day is normal. Prior to this fault occurs only occasionally, recent high frequency, appear almost every day.
Check Analysis: To further examine the vehicle, the process first requires a brief understanding of the remote operating vehicle. Signal from the remote control car with a 2-way, i.e., an infrared signal and a radio signal, two kinds of signals, received from the key fob issued by the front and rear window antenna amplifier door handle, and then transferred to the control unit OCP roof or front door the control unit, the control unit or the roof of the front door then the remote unit transmits a control signal to the cAN bus, the electronic ignition signal after receiving the check into the EIS recognized, when the recognized access authorization, via the cAN bus to transmit EIS ldquo; unlock rdquo; command, PSE pneumatic control unit receiving the command, the pneumatic driving means to unlock the door, then control antitheft released. Clear working process, the analysis of possible points of failure in the following areas.
(1) a failure occurs in the cold car every time, and the power supply system problems (including remote control battery, the vehicle body control system power supply, etc.) in the cold car prone, if the power supply is not normally, it will make the central locking is not working properly.
(2) anti-theft system is not working properly, or driving authorization system intermittent errors.
(3) the cold car, vehicle electrical control unit, etc. may also fail. Since there are two kinds of car remote control signal, i.e., an infrared signal and a radio signal, which is even a problem receiving a signal, another signal is also able to work, since it is now remote no response, indicating that the problem may be the signal processing and command activation phase, and the signal receiving portion is unlikely to go wrong. Thus the focus is locked on suspect PSE EIS electronic pneumatic control unit and an ignition switch.
According to the above idea, first check the power. Asking the user that, when operating the remote control, LED red LED remote end portion lights up, indicating that the remote control battery is sufficient. Further description of the user when the time to open the door by remote control, the vehicle can start smoothly, indicating battery power is sufficient, the possibility of failure of the power supply system can be ruled out. Benz DAS fault diagnostic apparatus is connected to a dedicated vehicle quickly tested are detected fault code and a number of remote control systems, with authorization and security system independent fault code, the fault code is not available since, only by observing each member the actual data to find the point of failure. As the car in the hot car is normal, it was decided to wait until then to test the next morning. In order to capture the data when the vehicle is locked, I advance DAS OBD diagnostic scan tool connected to the socket, the window opens. The next morning, central locking can not really unlocked.
into the fault diagnostic use PSE pneumatic control unit (PSE appearance frequency pneumatic control unit in the failure routine maintenance is relatively high, it is the control center for the whole car central locking actuator pneumatic member), no fault code stored in ldquo; central locking signal source rdquo; actual data, the first ldquo; central locking latest signal source 1rdquo; data to the PSE (pneumatic control unit) SN2ldquo; LOCKrdquo ;, indicating that data at this time or lock the car yesterday, and not just unlock signal is received. EIS read fault code, the fault code is not stored in the same, and are not related to the remote control data and information available in the actual data signal. EIS can not determine at this time is the failure to prevent the passage portion 2 receiving a remote control signal may also go wrong (because the door handle had previously encountered damage to the IR receiver, and the user does not notice it, or after subsequent OCP antenna At this time, the amplifier also fails, it will also symptoms of the car), so we went to the network to receive signals were examined.
using the scan tool into the roof control unit OCP, where the actual value of the supply voltage of 12.2 V, normally. The key detection result, the remote control lock button, the data can be displayed ldquo; into the key identification signal indicating that OCP rdquo ;, unlocking signal has been received, but while it receives the signal, but would not be transmitted to the CAN line it? And then proceeds to read the actual value of the left front door lock device control unit, a display ldquo; effective rdquo ;, indicating that the door control unit also receives the remote control signal. Since the two-way remote control signal can be received, and the CAN communication can be performed prior to the fault diagnostic tests by flash also between the control unit and the ignition switch start is normal, this also excludes the CAN bus and the problem with authorization possible failure will be locked in on the EIS electronic ignition switch.
due to the long cycle orders EIS expensive for sure, we had a ldquo; earth approach rdquo; to experiment. The key on the top cover plate infrared EIS socket with a slotted screwdriver into a number, with a hair dryer blowing hot air to the inside from the gap outlet, hot car in the simulation environment, when heated nearly 2 min, again by remote control button, I was able to successfully unlock the car door. Then determine the point of failure lies in the EIS electronic ignition switch.
FIG.
Solution: Remove the EIS will, carefully open the housing, careful observation of solder elements, and finally found 4J74Y model chip ( BRIEF) Weld pin slightly. The re-Weld spot welding, after loading the next day again, the result of the door can be smoothly opened remote troubleshooting.
reviewed: EIS 220 is earlier batch Benz central gateway chassis of the vehicle, the vehicle almost all signals between processing modules are exchanged via the CAN bus and the transmission EIS, EIS is also a power management center, responsible for many powered by the vehicle’s electrical functions, their work load, the heat is relatively high, so the resulting weld weld, and poor contact in the cold car.
(He Yuming)