Audi A6 car engine operation of the exhaust pipe a small amount of black smoke emitted, exhaust gas is faulty. After testing, the engine power was normal. OBD Diagnostic Tool connector perform self-diagnosis, the engine system has a fault code, reads "00561, mixture adjustment exceeds the limit." Executive DTC Clear function, the fault code is cleared. Fault analysis, there may be poor oxygen sensor performance. View the data flow (functional path 01-08-007), the idle mode of the 007 data block 1 zone data (mixed gas formation control value) for -25%, 2 District data (oxygen sensor signal voltage) of 0 809V. Under normal circumstances, the mixture formation control value should be within the range of -10%, 10%, and the fluctuation of the mixture of the mixture is slightly fluctuation with the fuel injection quantity.. -25% data shows that the engine control module attempts to reduce fuel injection, in order to control the concentration of mixture in normal range. The signal voltage of the oxygen sensor is 0 809V, partial rich mixture, in conformity with the fault phenomena of the smoke.
By the principle of fuel injection, the engine control module mainly according to engine speed signal, air flow sensor signal to determine the basic fuel injection quantity, use the Launch X-431 PAD or Launch X431 GDS tool to check air flow sensor. Select the feature path 01-08-002, view the air flow sensor data (4 area data). The air flow at idle speed is about 7.5 kg/s, which is obviously larger than the normal 2 0kg/s -4... The 2 zone data is the theory injection time (crankshaft to a circle), the 3 zone data for the engine a working cycle of injection time (actual injection time). The actual injection time is on the basis of theory of injection time correction of, should be twice fuel injection time and the car of the two injection time almost the same it proves that the theory of injection time is too long, after correction of the actual injection time shorter. When the fuel injection time correction exceed the limit, the failure code will occur 00561. The result of the above detection is that the cause of the fault is the air flow sensor signal is too big 6 replacement air flow sensor, the fault completely ruled out.
Since the air flow sensor signal in the car idling just too high, and in the part-load conditions and acceleration conditions are normal, and therefore less impact on the overall condition of the engine, fuel consumption is not significantly increased. In addition, by Autel MaxiSys Pro MS908P or Xtool PS2 dynamic data analysis process it can be seen, although the engine control module based on the oxygen sensor signal identification to the mixture is too thick, but no corresponding reduction in the fuel injection quantity so that the concentration of the mixture back to normal, the reason is, fuel injection depending on the amount of engine intake air, engine speed, oxygen sensor signal is only a feedback signal as a mixed gas under closed-loop control mode, the fuel injection quantity correction within a certain range.