Automotive fault diagnostic service is a very important tool (Figure 1), generally have several or all of the following features: ① read fault codes. ② clear fault codes. ③ read dynamic data flow engine. ④ oscilloscope function. ⑤ element actuation test. ⑥ matching, and other settings and encoding functions. ⑦ English-Chinese dictionary, calculator and other auxiliary functions. Most of the scan tool comes with instruction manual and follow the instructions easy to operate. In general the following steps: Locate the diagnostic socket in the car; use the appropriate diagnostic interface; according to model, enter the appropriate diagnostic system; read fault codes; view the data stream; clear DTCs after diagnosis maintenance.
Although the use of fault diagnostic method is relatively simple, but should give full play to the functions of the instrument, quickly identify the fault, maintenance personnel in use should be noted that there are some places, make some notes below.
1. Symptom fault content and combining the analysis to quickly determine where the failure cause
Use fault diagnostic trouble code query function, electronic control system failure can be a vehicle for scanning. In most cases, the fault records are not the Cause. But the content of the fault record, gives us scope to determine the fault location, combined with the failure phenomena and other laboratory examinations, you can quickly troubleshoot in this example.
figure Fault 1: a 2004 annual Passat B5 1.8T sedan, because not easy to start pit for repairs. Use the scan tool V.A.G1552 into the engine electronic control system to be checked (Figure 2), we found two faults, namely, intake air temperature sensor is shorted to ground or open circuit, and a variable intake control valve is open or shorted. Get the value of the constant flow of the intake air temperature is short-circuited by reading data, it can indeed determine the intake air temperature sensor is short-circuited. Hard acceleration, you can see the variable intake valve does not change the operation of the intake path. Multimeter measuring voltage block further use of the intake air temperature sensor plug input operating voltage of 12 V, while the standard value should be 5 V; simultaneously measured variable intake valve plug operating voltage of 5 V, while the standard value should be 12 V battery voltage. Through the above examination, and then control the color line in the circuit diagram of two elements, the cause of the fault quickly found: the original is two plug elements as each plug inserted the wrong cause the failure.
Tool:LAUNCH X431 5C
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