(1) Fault symptoms: The chassis model of this car is E90, equipped with an N46 engine. The fault 

symptoms are as follows: After starting the engine, the engine fault light on the instrument panel keeps 

lighting up, and the vehicle cannot accelerate.  

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(2) Diagnosis and maintenance After starting the engine, the idling condition is stable, but the yellow 

EML warning light (i.e. engine failure warning light) on the instrument panel keeps lighting up. When 

accelerating, the performance is very poor. Even if the accelerator pedal is pressed to the bottom, the 

speed is difficult to increase. Connect the diagnostic instrument for self-diagnosis. The engine system 

has two fault codes. The content is shown in Table 1-5.

  Preliminary judgment is that the fault is related 

to the electronic valve servo motor. The electric motor is installed on the valve cover and is directly 

controlled by the engine control module, as shown in Figure 1-27.

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  Unplug the wiring harness plug of 

the electronic valve motor and measure the resistance of the electronic valve servo motor. It is 0.1Ω.

  Since there is no standard resistance value, I don't know whether the resistance is normal, so it is 

impossible to judge whether the electronic valve servo motor is normal. Continue to check other parts.

  The engine control module, electronic valve motor relay, and fuse F1 are all installed in the electric 

control box on the left side of the engine compartment. Check the electronic valve motor relay and fuse 

F1, both are normal. Unplug the wiring harness plug of the engine control module and check the wiring 

connection with the electronic valve servo motor. It is normal. Installed the above related components, 

cleared the fault code, and tested the car, but the fault persisted. Check the fault information again, and 

the fault code 2A67 appears again. Why does the "short circuit to negative" fault message always 

appear? It seems that this is the key to maintenance, so I unplugged the wiring harness plug of the 

electronic valve servo motor and re-diagnosed the self-diagnosis. This time I made a new discovery: 

Although the fault code is still 2A67, the content has changed and it has become "Engine Wire" "Short 

circuit" indicates that the fault has nothing to do with the engine control module and its wiring. Unplug 

the wiring harness plug of the electronic valve servo motor, connect a test light with basically the same 

power, start the engine, and the test light flashes. After querying the fault information, the nature of the 

fault code 2A67 changed to non-existent, and the fault code 2A6B reappeared, which indicated that the 

electronic valve servo motor performance was poor. Replace it and eliminate the fault completely. 

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 (3) Summary The causes of faults related to fault code 2A67 include: poor connection of the wires or 

harness plugs of the electronic valve servo motor, damage to the electronic valve servo motor, and 

damage to the engine control module. Be very cautious when judging that the engine control module is 

damaged and do not replace it easily. The key point of the maintenance work in this example is to 

understand the meaning of fault code 2A67, and fault code 2A6B is a joint fault code. As long as the 

related problems of fault code 2A67 are solved, the problem of fault code 2A6B will naturally be 

solved. By unplugging and plugging the electronic valve Analyzing the meaning of the fault code 

through the wiring harness plug of the servo motor is the key to maintenance work.