INSPECTION PROCEDURE USING AN OSCILLOSCOPE
2018 / ECLIPSE CROSS / EC - Workshop Manual
13 -FUEL > 13A-DIRECT INJECTION AND MULTIPOINT FUEL INJECTION (DI AND MPI) > TROUBLESHOOTING > INSPECTION PROCEDURE USING AN OSCILLOSCOPE
The output signals of the sensors and the conditions of the actuation signals of the actuators can be inspected visually by observing the waveforms on the oscilloscope.
 
 
INLET CAMSHAFT POSITION SENSOR AND CRANK ANGLE SENSOR
 
 
Measurement Method
 
1. Disconnect the inlet camshaft position sensor connector and connect the special tool test harness (MB991709) in between (All terminals should be connected).
2. Connect the oscilloscope special pattern pickup to inlet camshaft position sensor terminal No. 2 (always mate all terminals).
3. Disconnect the crank angle sensor connector and connect the special tool Test harness (MB991709) in between.
4. Connect the oscilloscope special patterns pickup to crank angle sensor terminal No. 1 (always mate all terminals).
 
 
 
Standard Wave Pattern
Observation conditionCrank angle sensor and inlet camshaft position sensor
Selector switch of special patterns pickup× 1
AC-GND-DCDC
TIME/DIV.50 ms
VOLTS/DIV.5 V
EngineIdle
 
 
 
Description of Wave Patterns
  • The inlet camshaft position sensor serves as to detect the compression top dead centre of each cylinder. By observing this signal simultaneously with the crank angle sensor signal, it is possible to identify each cylinder.
  • The crank angle sensor is used to detect the crank angle of each cylinder. While the engine revolves for two cycles, 72 pieces of the crank angle sensor High signal (including any missing) will be output.
  • The engine-ECU carries out the engine control, using the fall signal (from 5 to 0 V) of the crank angle sensor. The rise signal (from 0 to 5 V) position does not affect the control.
 
 
Wave Pattern Observation Points
  • Verify that the sensor signal frequency increases as the engine speed rises.
 
 
Examples of Abnormal Wave Patterns
 
 
  • Example 1
  • Wave pattern characteristics
    • Rectangular wave will be output while the engine is not started.
    Cause of problem
    • Failed sensor interface
  • Example 2
  • Wave pattern characteristics
    • Wave pattern is displaced in the forward or backward.
    Cause of problem
    • Loose timing chain
    • Abnormal sensing section
 
 
 
 
EXHAUST CAMSHAFT POSITION SENSOR AND CRANK ANGLE SENSOR
 
 
Measurement Method
 
1. Disconnect the exhaust camshaft position sensor connector and connect the special tool test harness (MB991709) in between (All terminals should be connected).
2. Connect the oscilloscope special pattern pickup to exhaust camshaft position sensor terminal No. 2 (always mate all terminals).
3. Disconnect the crank angle sensor connector and connect the special tool Test harness (MB991709) in between.
4. Connect the oscilloscope special patterns pickup to crank angle sensor terminal No. 1 (always mate all terminals).
 

 
 
Standard Wave Pattern
Observation conditionCrank angle sensor and exhaust camshaft position sensor
Selector switch of special patterns pickup× 1
AC-GND-DCDC
TIME/DIV.50 ms
VOLTS/DIV.5 V
EngineIdle

 
 

 
 
Description of Wave Patterns
  • The exhaust camshaft position sensor serves as to detect the position of the exhaust camshaft and outputs one pulse per revolution of camshaft corresponding to the cut provided on the exhaust-side camshaft.
  • Whether retardation or advance can be defined as a more or less difference in time from when the crank angle sensor output wave falls to when the exhaust camshaft position sensor output wave rises or falls.
    noteAt a maximum retardation the fall of the exhaust camshaft position sensor output wave retards approximately 20°.
 
 
Wave Pattern Observation Points
  • Verify that, toward the engine speed of 2,500 r/min, time difference T from when the crank angle sensor output wave falls to when the exhaust camshaft position sensor output wave falls becomes less.
 
 
Examples of Abnormal Wave Patterns
 
 
  • Example 1
  • Wave pattern characteristics
    • Rectangular wave will be output while the engine is not started.
    Cause of problem
    • Failed sensor interface
  • Example 2
  • Wave pattern characteristics
    • Wave pattern is displaced in the forward or backward.
    Cause of problem
    • Loose timing chain
    • Abnormal sensing section
 
 
 
 
INJECTOR
 
 
Measurement Method
 
1. Disconnect the injector connector, and then connect the special tool Test harness (MB991658) in between (All terminals should be connected).
2. Connect the oscilloscope special patterns pickup to terminal No. 2 of the injector connector.
 
 
 
Standard Wave Pattern
Observation conditionInjector
Selector switch of special patterns pickup× 10
AC-GND-DCDC
TIME/DIV.0.5 ms
VOLTS/DIV.1 V
EngineIdle
 
 
 
Description of Wave Patterns
  • Normally the power supply voltage is shown. When the engine-ECU outputs the injector drive signal ON, the voltage falls to approximately 0 V during the period of the signal ON. (See Point B.)
  • When the engine-ECU stops the output of the injector drive signal, the voltage peak appears due to the counter electromotive force of the coil. (See Point A.) And then the power supply voltage returns to its normal value.
  • Injector operation time: fuel injection period determined by engine-ECU according to various sensor output values. Injector operation time = effective injection period + invalid injection period (invalid injection period: compensation of injector response delay due to decrease in power supply voltage)
  • Counter electromotive force of solenoid coil: the counter electromotive force is created in the injector coil when the engine-ECU stops the output of the injector drive signal.
  • Power supply voltage: the power supply voltage is shown when the engine-ECU stops the output of the injector drive signal ON. If this supply voltage is low, the injector operation time becomes longer as the invalid injection time becomes longer.
 
 
Wave Pattern Observation Points
  • Point A: The level of counter electromotive force of solenoid coil:
Solenoid coil counter electromotive force is low or doesn't appear at all.Short-circuit in the injector solenoid
 
  • Point B: Injector operation time
Operation timeConsistent with the displayed time on M.U.T.-IIISE.
Force an excessive acceleration.The drive period will once extend greatly, then will be settled to that corresponding to the engine speed.
 
 
 
 
IGNITION COIL (POWER TRANSISTOR CONTROL SIGNAL)
 
 
Measurement Method
 
1. Disconnect the ignition coil connector, and then connect the special tool test harness (MB991658) in between (Always mate all the terminals.)
2. Connect the oscilloscope special patterns pickup to terminal No. 1 of the ignition coil connector.
3. To verify the ignition advance angle, observe it simultaneously with the crank angle sensor output signals.
 

 
 
Standard Wave Pattern
Observation conditionCrank angle sensor and power transistor control signal
Selector switch of special patterns pickup× 1
AC-GND-DCDC
TIME/DIV.50 ms
VOLTS/DIV.5 V
EngineIdle
 
 
 
 
Description of Wave Patterns
  • Power transistor ON condition:
    An interval when the power transistor is ON and the primary side of ignition coil is conducted (referred to as "dwell interval") This conduction period gets longer if the battery voltage is low or vice versa so that the primary voltage at ignition can be controlled to a constant level.
  • Power transistor OFF condition:
    This interval corresponds to when the power transistor is OFF and the power transistor drive signal is not output from the engine-ECU.
 
 
Wave Pattern Observation Points
  • Verify that the power transistor control signal (ignition timing) advances as the engine speed increases.
 
 
Examples of Abnormal Wave Pattern
 
  • Wave pattern characteristics
    • The voltage is low.
  • Cause of problem
    • Open-circuit in the ignition primary circuit.