(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.
