Failure phenomenon: a new 2008 annual Shanghai Volkswagen Santana sedan, equipped BAS engine, mileage 30000 km. Users reflect the car appeared to accelerate in traveling often slow, EPC light on the phenomenon, sometimes even turn off not start.
check analysis: take the car after a preliminary examination, found no fault phenomenon reflected by the user. VAG1552 connected fault diagnostic, read fault code is 16705 (ignition / distributor, the engine speed signal tolerance) and 16706 (ignition / distributor, no engine speed signal, occasional), after clearing the fault code test, never showed failure, have had to PDI. The next day users complained that the vehicle can not be started, the maintenance personnel to the scene and found barely able to start the vehicle, but the engine shake severe, EPC lights. Read fault codes or diagnostic fault with 16705, which shows a poor engine speed sensor signal G28. But G28 is faulty, it should not be started, start now, indicating that there are other problems.
connected to the scan tool, clear fault code, together with the user road test. Fault has not appeared, but found that the data streams have varying degrees of fire in 01-08-014 / 015/016 each cylinder group, but no more than 6 times. Decided to start to solve the fire problems, it should take into account the spark plugs, ignition coil and high voltage while the probability of failure is very small, in which the possibility of ignition coil failure of the largest, and often start-up difficulties also confirmed this point. After replacing the ignition coil test, fault no longer occurs, then let the user to drive away, whether the failure to observe again in use.
The next day users complained that the vehicle appeared to accelerate the slow, EPC light on the phenomenon. After the pick, find fault has disappeared. After testing or fault code 16705, there is still a road test fire phenomenon. At this point the user reflects a case, the fault is go away when driving on the highway. Based on this clue conduct the road test, it was found that the speed exceeds 60 km / h when the vehicle is normal, but at low speeds the car occasional Dayton phenomenon, but different from ordinary fire, the car seems to be stalling after being dragged feeling. In order to completely eliminate the problem of fire, spark plugs, high-voltage, throttle body and also a Hall sensor replacement, and cleaning of engine deposits, but the fault persists.
Next, according to itTip check barrier code with G28-related parts. Remove the transmission, a ring gear check found no abnormalities, replacing part of an engine control unit and G28 harness, and then test the fault persists, and more serious. At this point repairs deadlocked.
due to a failure to sporadic, maintenance staff last resort, can only test for a long time, but later we found a fault occurred in the corner. To verify this finding, maintenance personnel on a playground frequent cornering, and sure enough there was a failure in a row, there are several or even turn off. Thus the fault coverage is defined in the region of the steering-related components of system activity, the steering column portion is first thought. Remove the instrument panel lower shield, an accelerator pedal sensor harness found in contact with the steering shaft has been worn, is in a critical state to ground. At this time, the flame artificially this grounding line, the engine shake violently.
troubleshooting: after the accelerator pedal sensor harness broken properly handled, failure to completely eliminate.
reviewed: in addition to conventional line fault inspection method, inspection method should be employed specifically for line faults, such as a wide range pulling line (not limited to the suspected site), so it is possible to artificially to reproduce the failure to find the point of failure as soon as possible. The service is only based on the results of fault diagnostic testing, according to the G28 engine misfire and poor signal these two ideas to diagnose faults, while ignoring the failures are sporadic this feature, special methods to solve the fault line did not take, so go detour. Random failure occurs, it is the outstanding feature of line faults, and to make timely qualitative, in order to take appropriate countermeasures. Encountered this kind of problem is to make the failure to reproduce the key, the only way to find the real point of failure. Before finding the fault point, the method using a large number of replacement parts is not desirable.
(female construction only)