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Summary of several common faults and diagnosis of Mercedes Benz

2021-08-26 15:16:28 Wechat automobile

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1、 The panoramic sunroof won't close  

【 Troubleshooting 】: The function check found that the sunroof is in the ventilation position , When pressing the sunroof switch, you will hear an obvious abnormal noise from the sunroof motor , And the skylight remains in its original position . Other functions are normal . Connect the diagnostic instrument for quick test , The sunroof control module does not set a fault code .

【 Cause analysis 】

1) There is foreign matter stuck in the sliding rail of the sunroof ;

2) The sunroof slide rail is deformed 、 Mechanical damage such as fracture ;

3) Too much resistance due to lack of lubrication or too much dust on the sliding rail of the sunroof ;

4) Sunroof standardization is not successful ;

5) Sunroof motor damaged ;

6) The sunroof control module is damaged .

Through comprehensive analysis, the cause of the fault is that the size of the chute on both sides of the skylight is out of tolerance , Too narrow , Cause excessive resistance between the sunroof glass and the rear support of the left and right sliding rails of the sunroof , Finally, the driving gear of sunroof motor and steel cable will overload and slip , Make a rattling noise , Deformation and wear of gears and cables .

【 Solution 】: Replace the sunroof glass 、 After the sunroof motor and the left and right sliding rails, the sunroof is standardized , Troubleshooting .

2、 Mercedes E260 The front right seat will not move

【 Troubleshooting 】: First, check the function , Operate the front right seat switch , I found that the front right seat wouldn't move in all directions , The front left seat can be adjusted normally . Connect the diagnostic instrument , Read the fault code of the front right seat control module . Open the seat control module housing of the faulty vehicle , It was found that there were serious ablation marks on the printed circuit board , A simple analysis shows that , The cause of serious ablation of the circuit board must be a short circuit somewhere , So I decided to check the seat circuit , Finally, it was found that a red harness was worn and grounded at the junction of cushion and backrest , After looking up the circuit diagram, it is confirmed that it is the power supply harness from the seat control module to the lumbar support adjustment control module .

【 Solution 】: Wrap the worn harness , And replace the front right seat control module , Clear the fault code , The seat adjustment is normal .

3、 Four wheel positioning

【 Troubleshooting 】: After the four-wheel alignment value is out of alignment , The vehicle will feel heavy when turning , Poor reversion , The tire will have eccentric wear . According to maintenance statistics W140 A car with a chassis usually runs 60000 to 70000 When it's about 100 kilometers , Due to the damage of the lower suspension rubber sleeve, the positioning value is inaccurate .

【 Solution 】: In case of the above faults , The suspension rubber sleeve must be replaced in the repair shop in time , Adjust the four-wheel alignment .

4 、 Replace the spark plug

【 Troubleshooting 】: After the performance of the spark plug becomes worse , When you are driving, you will feel that the engine power is insufficient 、 Rapidly accelerate the car and send out a sound along with the exhaust pipe “ A sudden 、 A sudden ” The sound , Engine jitter at idle speed .

【 Solution 】: It is recommended that every time driving 3 Ten thousand kilometers to the repair shop to check the spark plug , Replace if necessary .

5、 Symptoms after dirty throttle body

【 Troubleshooting 】: Mercedes W140 The car's throttle is running 20000 When it's about 100 kilometers , Due to air quality , There will be a lot of dirt at the shut-off valve , When dirt accumulates to a certain thickness , The engine will not start easily , Abnormal idle speed after driving , Flameout during driving , At this time, the throttle needs to be cleaned .

【 Solution 】: After cleaning, it can reach the standard through the setting of the original diagnostic instrument .

6、 Do not disassemble and clean the fuel injector

【 Troubleshooting 】: After the fuel injection nozzle is dirty , The engine will have difficulty starting 、 Power down 、 Slow acceleration 、 Shivering at idle speed 、 Black smoke 、 The exhaust gas exceeds the standard 、 In severe cases, the engine will not start .

【 Solution 】: Clean the fuel injection nozzle without disassembly , At the same time, the carbon deposit on the combustion chamber and the top of the piston can be cleaned . It is recommended that every time the vehicle runs 20000 Km for a disassembly free cleaning . This can also prevent the carbon deposit in the intake system from being too thick .


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