Oscilloscope Patterns and Waveforms

INSPECTION PROCEDURE USING AN OSCILLOSCOPE

INTAKE CAMSHAFT POSITION SENSOR AND CRANKSHAFT POSITION SENSOR









Required Special Tools:

- MB991709: Test Harness

- MB992110: Power Plant ECU Check Harness

Measurement Method

1. Disconnect the intake camshaft position sensor connector, and connect the test harness special tool (MB991709) between the separated connector (All terminals should be connected).

2. Connect the oscilloscope probe to intake camshaft position sensor connector terminal No. 3.

3. Disconnect the crankshaft position sensor connector, and connect the test harness special tool (MB991709) between the separated connector (All terminals should be connected).

4. Connect the oscilloscope probe to crankshaft position sensor connector terminal No. 3.

Alternate method





1. Disconnect all ECM connectors. Connect the check harness special tool (MB992110) between the separated connectors.





2. Connect the oscilloscope to check harness terminal No. 14. (Check the intake camshaft position sensor signal wave pattern.)
3. Connect the oscilloscope to check harness terminal No. 8. (Check the crankshaft position sensor signal wave pattern.)

Standard Wave Pattern






Wave Pattern Observation Points
1. Verify that the sensor signal frequency increase as the engine speed rises.





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 chain.

- Abnormality in sensor disc.
Wave
pattern characteristics
- Wave pattern is displaced to the left or right.

EXHAUST CAMSHAFT POSITION SENSOR AND CRANKSHAFT POSITION SENSOR









Required Special Tools:

- MB991709: Test Harness

- MB992110: Power Plant ECU Check Harness

Measurement Method

1. Disconnect the exhaust camshaft position sensor connector, and connect the test harness special tool (MB991709) between the separated connector (All terminals should be connected).

2. Connect the oscilloscope probe to exhaust camshaft position sensor connector terminal No. 3.

3. Disconnect the crankshaft position sensor connector, and connect the test harness special tool (MB991709) between the separated connector (All terminals should be connected).

4. Connect the oscilloscope probe to crankshaft position sensor connector terminal No. 3.

Alternate method





1. Disconnect all ECM connectors. Connect the check harness special tool (MB992110) between the separated connectors.





2. Connect the oscilloscope to check harness terminal No. 7. (Check the exhaust camshaft position sensor signal wave pattern.)
3. Connect the oscilloscope to check harness terminal No. 8. (Check the crankshaft position sensor signal wave pattern.)

Standard Wave Pattern






Wave Pattern Observation Points

- Verify that the relative position of the exhaust camshaft position sensor's output wave changes when the low load operation changes to the high load operation.





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 chain.

- Abnormality in sensor disc.
Wave
pattern characteristics
- Wave pattern is displaced to the left or right.

INJECTOR

Required Special Tools:

- MB991658: Test Harness

- MB992110: Power Plant ECU Check Harness





Measurement Method
2. Disconnect the injector connector, and connect the test harness special tool (MB991658) between the separated connector. (All terminals should be connected.)

3. Connect the oscilloscope probe to injector connector terminal No. 2.









Alternate method
4. Disconnect all ECM connectors. Connect the check harness special tool (MB992110) between the separated connectors.

5. Connect the oscilloscope probe to each check harness connector terminal to analyze each cylinder:

- Terminal No. 2 for the number 1 cylinder.

- Terminal No. 3 for the number 2 cylinder.

- Terminal No. 18 for the number 3 cylinder.

- Terminal No. 19 for the number 4 cylinder.

Standard Wave Pattern






Wave Pattern Observation Points

Point A: Height of injector coil induced voltage.





Point B: Injector drive time









6. The injector drive time should be synchronized with the scan tool tester display.

7. When the engine is suddenly revved, the drive time will be greatly extended at first, but the drive time will soon return to original length.

EGR VALVE (STEPPER MOTOR)

Required Special Tools:

- MB991658: Test Harness

- MB992110: Power Plant ECU Check Harness

Measurement Method





1. Disconnect the EGR valve connector, and connect the test harness special tool (MB991658) between the separated connector (All terminals should be connected).
2. Connect the oscilloscope probe to the EGR valve connector terminal No. 1, terminal No. 3, terminal No. 4, terminal No. 6 respectively.

Alternate method





1. Disconnect all ECM connectors. Connect the check harness special tool (MB992110) between the separated connectors.





2. Connect the oscilloscope probe to check harness terminal No. 31, No. 32, No. 47 and No.
48.

Standard Wave Pattern






Wave Pattern Observation Points
8. Check that the standard wave pattern appears when the EGR valve is operating.

Point A: Presence or absence of induced electromotive force from the motor turning. (Refer to abnormal wave pattern.)





Point B: Height of coil back electromotive force











Examples of Abnormal Wave Patterns





Example 1

Cause of problem
- Malfunction of motor. (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 EGR valve and the ECM.
Wave
pattern characteristics
- Current is not supplied to the motor coil on the open circuit side. (Voltage does not drop to 0 volt.) Furthermore, the induced electromotive force wave pattern at the normal side is slightly different from the normal wave pattern.

IGNITION COIL AND IGNITION POWER TRANSISTOR

Required Special Tools:

- MB991658: Test Harness

- MB992110: Power Plant ECU Check Harness





Measurement Method
9. Disconnect the ignition coil connector, and connect test harness special tool (MB991658) between the separated connector. (All terminals should be connected.)

10. Connect the oscilloscope probe to ignition coil connector terminal No. 2.

Alternate method









11. Disconnect all ECM connectors. Connect the check harness special tool (MB992110) between the separated connectors.

12. Connect the oscilloscope probe to each check harness connector terminal to analyze each cylinder:

- Terminal No. 4 for the number 1 cylinder.

- Terminal No. 5 for the number 2 cylinder.

- Terminal No. 20 for the number 3 cylinder.

- Terminal No. 21 for the number 4 cylinder.

Standard Wave Pattern






Wave Pattern Observation Points

Point: The power transistor control signal (ignition timing) is advanced when the engine speed is increased.











Examples of Abnormal Wave Patterns





Example 1 (Wave pattern during engine cranking)

Cause of problem
- Open-circuit in ignition primary circuit
Wave
pattern characteristics
- Voltage value is too low.