They say that the shell does not fall twice into the same funnel, bearing in mind that different malfunctions cannot occur several times in a row in the same node. Apparently, this did not apply to the Mitsubishi Eclipse 2.4 2003 4G64 car with a complaint about unstable operation and the complete inability to start a warm car.
Scanning TPA showed a saved error P0340 Camshaft Position Sensor A Circuit Malfunction (Bank 1 or Single Sensor) This error is common, and at first the repair did not seem difficult. The cold engine stably started and worked. However, if you turn off the warmed-up engine and try to start it again, it will not start. Here’s what the Autoscope on a hot motor on the Camshaft Position Sensor signal wire showed:
The output voltage of the lower level of the Hall sensor with heating was very different from 0 volts. And at the operating temperature of the engine it became equal to 4 volts. The ECM did not recognize such a signal and did not open the nozzles. This malfunction is quite common. Therefore, without hesitation, the new Camshaft Position Sensor was ordered..
When the new Camshaft Position Sensor was installed on the car, the problem of starting a hot motor passed, but a new defect appeared. Wince, and sporadic failure not related to engine operation. Already in some doubts about the correctness of their decisions, using the Autoscope, the signal was again recorded on the signal wire of the Camshaft Position Sensor:
The recorded waveform shows that there is interference on the signal wire of the Camshaft Position Sensor, which can be caused either by a defect in the mass wire of the sensor power supply or by a defect in the Camshaft Position Sensor itself. Checking the wiring defect did not reveal, and again it was decided to replace the Camshaft Position Sensor.
Installing another Camshaft Position Sensor changed the symptoms of the disease, but Eclipse did not cure. Now the car steadily started up and worked at any engine temperature, but only at revs XX. It was enough to press the gas pedal, pops and crashes began. To understand the nature of the defect, 4 signals were recorded by the Autoscope.
1. Camshaft Position Sensor.
2. Injector 3-4.
3. Injector 1-2.
At engine speed XX, the engine runs smoothly:
However, when you press the gas pedal, everything changes. Injectors of 3-4 cylinders are closed almost all the time and only sometimes open. And nozzles of 1-2 cylinders are almost completely open, supplying a large amount of fuel to the cylinders, and only occasionally close. At the same time, there are no visible failures in the Camshaft Position Sensor. Ignition is also supplied without visible malfunctions:
To understand the cause of the failure, compare the signals of the installed Camshaft Position Sensor and the reference. As a reference, you can use the first Camshaft Position Sensor, with which the car came to the service, and which worked fine while it was cold.
What signal to take as a reference point? It would be most logical to use TDC. The TDC signal can be obtained using a pressure sensor screwed into the cylinder. However, installing a DD (pressure sensor) in one of the cylinders will turn it off, which will change the mode of operation of the motor. It is better to use the ignition signal in the 1st cylinder as the coordinate axis in XX mode. Ignition of the mixture in the XX mode occurs approximately 10 degrees to the TDC point and fluctuates in the range of + -5 degrees. Since the displacement of the SPD occurs relative to the Crankshaft Position Sensor, and we are interested in the offset of the Crankshaft Position Sensor relative to the Camshaft Position Sensor, the oscillations of the SPD are not important for us.
This is what the “reference” waveform obtained using the Autoscope looks like:
Channel 1 – Camshaft Position Sensor.
Channel 2 – Crankshaft Position Sensor.
Channel 3 – IGN.
Having set the coordinate so that between the signals of the spark of the 1st cylinder in the adjacent engine cycles of 720 degrees, we determine the shift of the Camshaft Position Sensor signal relative to the Crankshaft Position Sensor.
The screenshot below shows that the transition from low to high level Camshaft Position Sensor performs approximately 53 degrees before switching Crankshaft Position Sensor. We shoot the same waveform using the third Camshaft Position Sensor, which crashes when the speed increases:
Here, the Camshaft Position Sensor moves from low to high approximately 37 degrees before switching the Crankshaft Position Sensor. Thus, the delay in switching on a defective Camshaft Position Sensor is 16 degrees or 3 milliseconds, which does not affect the low engine speed. At high speeds, a 3 ms delay in the Camshaft Position Sensor introduces a malfunction in the calculation of the moment the nozzles open, preventing normal motor operation.
Camshaft Position Sensor’s next replacement finally brought a recovery to the car.
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