Mass air flow sensor
1. Connect the oscilloscope probe (motor tester) to the conclusion "3" connector of the mass air flow sensor or to the corresponding output of the electronic engine control unit.
2. Compare the waveform of the sensor on the oscilloscope with the picture when the engine is running at idle speed.
Division value: X - 5 ms / d., Y - 2 V / d.
3. Check that there is a period reduction "T" and an increase in the signal frequency with an increase in the crankshaft speed (those. the amount of air entering the cylinders).
4. Possible deviations from the normal waveform.
A) Due to a fault in the circuits between the mass air flow sensor and the engine control unit, the signal appears in the form of rectangular pulses, even if the engine is not running.
b) Due to damage to the mass air flow sensor, the signal is present in the form of an unstable variable frequency curve. However, if high voltage leakage occurs when the engine speed is increased (from the ignition system), then temporary distortion will appear on the curve, even with a working mass air flow sensor.
Camshaft position sensor and crankshaft position sensor
1. Connect an oscilloscope to the camshaft and crankshaft position sensors to check the waveform (see pin number in figure).
Engine 4G15.
Engine 4G93.
2. Compare the waveform of the sensor on the oscilloscope with the waveform in the corresponding figure when the engine is idling. Check if period reduction occurs "T" with an increase in engine speed.
Normal waveform of camshaft position sensor and crankshaft position sensor. (1) - crankshaft position sensor, (2) - camshaft position sensor. Division value: X -10 ms / d., Y - 2 V / d.
Note: Two revolutions of the crankshaft correspond to one revolution of the camshaft.
3. Possible deviations from the normal waveform.
A) Due to a fault in the circuits between the sensor and the engine control unit, the signal appears in the form of short pulses, even if the engine is not running.
b) Due to a loose timing belt or a faulty sensor rotor, the rectangular pulses will shift to the right or left.
Nozzles
1. Connect the probe of the motor-tester to the terminals of the connector of the electronic unit with the engine and the variator corresponding to injector No. 1 and the signal when the injector circuit is opened (conclusions "1" And "63").
2. Then check injectors No. 2, No. 3, No. 4 in the same way.
Conclusions of the electronic unit:
- Nozzle #2 — "9" And "63"
- Nozzle #3 — "24" And "63"
- Nozzle No. 4 - "2" And "63"
3. Check the conformity of the shape and duration of the injector control signal with the figure when the engine is idling.
1) - signal when the circuit is opened» injectors, (2) - signal at the injector. Division value: X - 25 ms / d., Y - 2 V / d.
4. Pay attention to the following points when checking the signal.
A) With a sharp press on the accelerator pedal, the duration of the injector control pulse will first increase significantly, but will not soon return to its normal form.
b) Check that the injector full circuit open signal is synchronized with each injector control signal.
Ignition coil and power transistor
1. Connect the motor-tester sensor; to the conclusion "3" ignition coil connector or terminals of the electronic unit, control, corresponding to coils No. 1 - 4.
Conclusions of the electronic unit:
- Coil #1 — "11"
- Coil #2 - "12"
- Coil #3 — "3f"
- Coil #4 - "31"
2. Check the conformity of the forms, the signal with the drawing when the engine is running in the specified mode.
Engine operating mode - approximately 1200 rpm
Note: When observing the signal, pay attention to the condition of the voltage rise section and the maximum voltage.
(1) - crankshaft position sensor signal, (2) - power transistor signal. Division value: X - 10 ms/d.; Y - 2 B/d.; T is the time of rotation of the cub shaft by 180°; in the ignition timing.
3. In the normal state, a signal with a voltage rise in the upper right part (voltage rise from about "D" before "E").
Rated value:
- "D" - approximately 2.0 V
- "E" - approximately 4.5 V
4. Examples of deviations from the normal waveform (signal form when the crankshaft of the engine is scrolled by a starter).
A) Due to an open circuit, in the primary winding of the ignition coil, rectangular signals (there is no upper right section of voltage growth), and the maximum voltage reaches only the specified value "D".
b) Due to a malfunction of the power transistor when the power transistor is turned on (position "ON") supply voltage occurs (X / in).
EGR valve actuator
1. Connect the oscilloscope probe (motor tester) to conclusions "4" And "6", "1" And "3" the EGR solenoid valve connector or the corresponding connector terminals of the engine control unit.
2. Check that the normal waveform appears while the stepper motor is running (see picture) in the mode of increasing the frequency of rotation of the crankshaft of the engine (when pressing the accelerator pedal).
Division value: X - 25 ms / div., Y - 1 V / div. Region "A" - counter-EMF that occurs when the motor rotates. Region "IN" -EMF self-induction in the winding.
3. Pay attention to the following points when observing the signal.
A) Dot "A" - the presence or absence of EMF induced during the rotation of the electric motor.
Note: if the electric motor is faulty, then the back-EMF does not occur when the electric motor rotates, or its value is very small.
b) Dot "IN" - the value of the EMF of self-induction (inductive ejection).
Note: if a short circuit occurs in the winding, then the self-induction EMF that occurs in the winding does not appear or its value is very small.
4. An example of a deviation from the normal waveform.
A) Due to a faulty stepper motor (does not work) back EMF does not appear when the motor rotates.
b) An open in the circuit between the stepper motor and the electronic engine control unit. When the circuit is broken, no current flows in the motor winding (voltage does not drop to 0 V). Note that the back-EMF signal generated when the motor is rotating (with a good stepper motor) only slightly different from the signal when the motor winding circuit is open.