A 2020 Benz E260 sedan with a mileage of about 5000km, equipped with a 48V electrical system and an M264 engine. The owner reported that the engine suddenly turned off during the driving process, and occasionally there was an abnormal phenomenon in which the gear was in the first gear but the engine speed reached 4000r/min.
Fault diagnosis: First, check the relevant information of the faulty car on the dealer management system DMS. The car has not been repaired before. Through communication with the owner, it was learned that the engine suddenly turned off when the car was decelerating at 10-20km/h and turning right, and at the same time the warning message of "Flame off!" was displayed on the instrument panel; restart the engine, the engine failure light on the instrument panel was always on. The fault has only occurred once so far. In addition, when driving at low speeds, the car also experienced an abnormal phenomenon that the engine speed would be as high as 4000r/min without stepping on or lightly stepping on the accelerator pedal in the first gear state, and the frequency of this failure was high, but the speed exceeded 60km/ This failure has not occurred in h. When the fault occurs, the abnormal rotation speed disappears after turning the shift paddle to upshift.
Next, test run. Start the engine, the engine fault light on the instrument panel is always on, no flameout phenomenon is found in the test run, and other functions are normal. Connected to the Mercedes-Benz special diagnostic instrument (XENTRY) to quickly test the faulty car. No-fault code is found in the engine control unit (Figure 1), but the start-generator (M1/10) has fault code P061 B00. If there are any complaints from customers To delete the fault code. There are also fault codes in the transmission control unit (Y3/8n4): P061B00-control unit torque calculation is faulty; P0A9200 a hybrid power system generator has a functional fault.
A pilot test was performed on the fault code of the start-generator control unit M1/10, and the result was that the fault code can be ignored and deleted, and a solution was provided, namely, to upgrade the control unit software.
The pilot test is performed on the two fault codes of the transmission control unit Y3/8n4, and the result is that the fault codes can be ignored and deleted.
According to the above-mentioned guided test results, a generator and a transmission control unit were programmed to start a generator, but no updated software version was found to eliminate the possibility of software failure.
According to the XENTRY results, the engine fault light is caused by the fault code of starting a generator control unit M1/10, but according to the fault phenomenon described by the car owner, both M1/10 and Y3/8n4 may cause the above fault phenomenon .
The faulty model is equipped with a 48V onboard electrical system, and an integrated starter-generator replaces the traditional 12V starter and generator. When starting, the 48V battery (G1/3) supplies power to the starting generator to start the engine; after starting, the starting generator can also use the energy from the 48V battery to generate torque to support the engine. The torque can be positive torque. (Support), it can also be negative torque (recovery), which can make the engine run more efficiently and store the excess energy in the 48V battery. Therefore, it is preliminarily judged that the possibility of abnormal phenomena such as engine stalling and speed of 1st gear up to 4 000r/min caused by sending an error message to ME by starting a generator is higher, and the start-generator is checked first.
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