How to solve the problem of BMW 318i having difficulty starting
(1) Fault symptoms: The chassis model is E46, equipped with an M43 engine. The fault symptoms are
as follows: the engine often has difficulty starting or even cannot start the car. In order to start the
engine, it is necessary to press the accelerator pedal to start, so that the engine can run.
(2) Diagnosis and maintenance: Confirm the fault symptoms and start the engine. Although the engine
has signs of running, it cannot run. Press the accelerator pedal to start, and the engine finally runs.
Observing the engine operating conditions, the idle speed is relatively stable and there is no sluggish
acceleration, indicating that the problem only occurs during the starting process. Use the diagnostic
instrument to perform self-diagnosis, select the “DME digital engine electronic servo control system
MS461″ item, and query the fault information. The fault code is 87, and the content is that the camshaft
position sensor signal is missing or untrustworthy, and the fault currently exists. Check the engine
operating data, see Table 1-2. All the above data are normal. Looking at the cylinder running
smoothness data, cylinders 2 and 3 are working in good condition and there is no ignition loss problem.
Cylinders 1 and 4 have a slight ignition loss, but it does not cause starting difficulties. Based on the
above inspection results, the nature of fault code 87 is that it currently exists, and the camshaft position
sensor or signal is most likely to be bad, so we focus on checking this sensor. The M43 engine is only
equipped with one camshaft position sensor, and its circuit diagram is shown in Figure 1 -25 shown.
Unplug the sensor’s wiring harness plug, turn on the ignition switch, and measure the terminal voltage
of the wiring harness plug. The power line terminal voltage is 12V, the signal line terminal voltage is
10V, and the ground wire terminal voltage is OV. All are normal, which means the fault is in the cam.
The shaft position sensor itself. Replace the sensor, clear the fault code, test drive, and troubleshoot
The status disappears and the maintenance work is completed.
(3) Summary The engine has two sensors related to speed and phase: one One is the crankshaft
position sensor located at the rear of the cylinder block; the other is the camshaft position sensor
located
at the front of the cylinder head. The camshaft position sensor is a Hall-type sensor that measures the
phase of the camshaft. The engine control module performs the full sequence fuel injection function
based on the camshaft position sensor signal to achieve optimal control of ignition timing and fuel
injection time. If the sensor fails, the engine control module activates the ignition loss identification
function, starts the emergency operation program, and only performs cylinder identification once.
Therefore, difficulty in starting will also occur, but there will be no obvious acceleration problems. The
camshaft position sensor of the M43 engine is relatively easy to damage. If a fault code related to the
sensor appears, it should usually be replaced.
