[13B] MULTIPORT FUEL INJECTION (MPI) <4G64> - - TROUBLESHOOTING - INSPECTION PROCEDURE USING OSCILLOSCOPE | PRINT PAGE / INDEX / PRIOR / NEXT

| INSPECTION PROCEDURE USING 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.
| AIR FLOW SENSOR
| Measurement Method
| Disconnect the air flow sensor connector, and connect the special tool Test harness (MB991709) in between (All terminals should be connected). Connect the oscilloscope special patterns pickup to air flow sensor connector terminal No. 3.
| Alternate Method (Test harness not available) Connect the oscilloscope special patterns pickup to engine-A/T-ECU terminal No. 65.
| Standard Wave Pattern
Observation conditions
Function | Special patterns
--- | ---
Pattern height | Low
Pattern selector | Display
Engine | Idling
| Wave Pattern Observation Points Check that cycle time T becomes shorter and the frequency increases when the engine speed is increased.
| Examples of Abnormal Wave Patterns
| Example 1 Cause of problem Sensor interface malfunction Wave pattern characteristics Rectangular wave pattern is output even when the engine is not started. Example 2 Cause of problem Damaged rectifier or vortex generation column Wave pattern characteristics Unstable wave pattern with non-uniform frequency. However, when an ignition leak occurs during acceleration, the wave pattern will be distorted temporarily, even if the air flow sensor is normal.
| CAMSHAFT POSITION SENSOR AND CRANK ANGLE SENSOR
| Measurement Method
| Disconnect the camshaft position sensor connector and connect the special tool Test harness (MB991709) in between (All terminals should be connected). Connect the oscilloscope special pattern pickup to camshaft position sensor terminal No. 2. Disconnect the crank angle sensor connector and connect the special tool Test harness (MD998478) in between. Connect the oscilloscope special patterns pickup to crank angle sensor terminal No. 2.
| Alternate Method (Test harness not available) Connect the oscilloscope special patterns pickup to engine-A/T-ECU terminal No. 56 (When checking the camshaft position sensor signal wave pattern). Connect the oscilloscope special patterns pickup to engine-A/T-ECU terminal No. 45 (When checking the crank angle sensor signal wave pattern).
| Standard Wave Pattern
Observation condition
Function | Special patterns
--- | ---
Pattern height | Low
Pattern selector | Display
Engine | Idling
| Wave Pattern Observation Points Check that cycle time T becomes shorter when the engine speed increases.
| Examples of Abnormal Wave Patterns
| Example 1 Cause of problem Sensor interface malfunction Wave pattern characteristics Rectangular wave pattern is output even when the engine is not started.
| Example 2 Cause of problem Loose timing belt Abnormality in sensor disk Wave pattern characteristics Wave pattern is displaced to the left or right.
| INJECTOR
| Measurement Method
| Disconnect the injector connector, and then connect the special tool Test harness set (MB991348) in between (All terminals should be connected). Connect the oscilloscope special patterns pickup to terminal No. 2 of the injector connector.
| Alternate Method (Test harness not available) Connect the oscilloscope special patterns pickup to engine-A/T-ECU terminal No. 1 (When checking the No. 1 cylinder). Connect the oscilloscope special patterns pickup to engine-A/T-ECU terminal No. 9 (When checking the No. 2 cylinder). Connect the oscilloscope special patterns pickup to engine-A/T-ECU terminal No. 24 (When checking the No. 3 cylinder). Connect the oscilloscope special patterns pickup to engine-A/T-ECU terminal No. 2 (When checking the No. 4 cylinder).
| Standard Wave Pattern
Observation conditions
Function | Special patterns
--- | ---
Pattern height | Variable
Variable knob | Adjust while viewing the wave pattern
Pattern selector | Display
Engine | Idling
| Wave Pattern Observation Points Point A: Height of solenoid back electromotive force
Contrast with standard wave pattern | Probable cause
--- | ---
Solenoid coil back electromotive force is low or doesn’t appear at all. | Short in the injector solenoid
| Point B: Injector drive time
| The injector drive time will be synchronized with the MUT-II tester display. When the engine is suddenly raced, the drive time will be greatly extended at first, but the drive time will soon match the engine speed.
| IDLE SPEED CONTROL SERVO (STEPPER MOTOR)
| Measurement Method
| Disconnect the idle speed control servo connector, and connect the special tool Test harness (MB991709) in between. Connect the oscilloscope special patterns pickup to the idle speed control servo-side connector terminal No. 1, No. 3, No. 4 and No. 6 respectively.
| Alternate Method (Test harness not available) Connect the oscilloscope special patterns pickup to engine-A/T-ECU terminal No. 14, connection terminal No. 15, connection terminal No. 28, and connection terminal No. 29 respectively.
| Standard Wave Pattern
Observation conditions
Function | Special patterns
--- | ---
Pattern height | High
Pattern selector | Display
Engine condition | When the engine coolant temperature is 20°C or below, turn the ignition switch from LOCK (OFF) position to ON (without starting the engine).
While the engine is idling, turn the A/C switch to ON.
Immediately after starting the warm engine.
| Wave pattern Observation Points Check that the standard wave pattern appears when the stepper motor is operating. Point A: Presence or absence of induced electromotive force from the motor turning (Refer to the abnormal wave pattern).
Contrast with standard wave pattern | Probable cause
--- | ---
Induced electromotive force does not appear or is extremely small. | Motor is malfunctioning
| Point B: Height of coil reverse electromotive force
Contrast with standard wave pattern | Probable cause
--- | ---
Coil reverse electromotive force does not appear or is extremely small. | Short in the coil
| Examples of Abnormal Wave Pattern
| Example 1 Cause of problem Motor is malfunctioning. (Motor is not operating.) Wave pattern characteristics Induced electromotive force from the motor turning does not appear.
| Example 2 Cause of problem Open circuit in the line between the stepper motor and the engine-A/T-ECU. Wave pattern characteristics Current is not supplied to the motor coil on the open circuit side (Voltage does not drop to 0 V). Furthermore, the induced electromotive force waveform at the normal side is slightly different from the normal waveform.
| IGNITION COIL AND POWER TRANSISTOR
| Measurement Method
| Disconnect the ignition coil connector, and connect the special tool Test harness set (MB991348) in between (All terminals should be connected). Connect the oscilloscope special patterns pickup to terminal No. 3 of each ignition coil connector in turn.
| Alternate Method (Test harness not available) Connect the oscilloscope special patterns pickup to engine-A/T-ECU terminal No. 11 (No. 1 - No. 4), connection terminal No. 12 (No. 2 - No.3) respectively.
| Standard Wave Pattern
Observation condition
Function | Special patterns
--- | ---
Pattern height | Low
Pattern selector | Display
Engine | Approximately 1,200 r/min
| Wave Pattern Observation Points Point: Condition of wave pattern build-up section and maximum voltage (Refer to abnormal wave pattern examples 1 and 2).
Condition of wave pattern build-up section and maximum voltage | Probable cause
--- | ---
Rises from approximately 2 V to approximately 4.5 V at the top-right | Normal
2 V rectangular wave | Open-circuit in ignition primary circuit
Rectangular wave at power voltage | Power transistor malfunction
| Examples of Abnormal Wave Patterns
| Example 1 Wave pattern during engine cranking Cause of problem Open-circuit in ignition primary circuit Wave pattern characteristics Top-right part of the build-up section cannot be seen, and voltage value is approximately 2 V too low.
| Example 2 Wave pattern during engine cranking Cause of problem Malfunction in power transistor Wave pattern characteristics Power voltage results when the power transistor is ON.

[13B] MULTIPORT FUEL INJECTION (MPI) <4G64> - - TROUBLESHOOTING - INSPECTION PROCEDURE USING OSCILLOSCOPE | PRINT PAGE / INDEX / PRIOR / NEXT

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