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 intermediate connector and connect the special tool Test harness (MB991658) 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. 71 (When checking the camshaft position sensor signal wave pattern).
- Connect the oscilloscope special patterns pickup to engine-A/T-ECU terminal No. 70 (When checking the crank angle sensor signal wave pattern).
Standard Wave Pattern
| Function |
Special patterns |
|---|---|
| Pattern height |
Low |
| Pattern selector |
Display |
| Engine speed |
Idle |
)
Wave Pattern Observation Points
Check that cycle time T becomes shorter when the engine speed increases.Examples of Abnormal Wave Patterns
)
- Example 1
- Sensor interface malfunction
Cause of problem
- Rectangular wave pattern is output even when the engine is not started.
Wave pattern characteristics
)
- Example 2
- Loose timing belt
- Abnormality in sensor disk
Cause of problem
- Wave pattern is displaced to the left or right.
Wave pattern characteristics
Measurement Method
)
- Disconnect the injector connector, and then connect the special tool Test harness set (MB991658) 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. 5 (When checking the No. 2 cylinder).
- Connect the oscilloscope special patterns pickup to engine-A/T-ECU terminal No. 14 (When checking the No. 3 cylinder).
- Connect the oscilloscope special patterns pickup to engine-A/T-ECU terminal No. 21 (When checking the No. 4 cylinder).
Standard Wave Pattern
| Function |
Special patterns |
|---|---|
| Pattern height |
Variable |
| Variable knob |
Adjust while viewing the wave pattern |
| Pattern selector |
Display |
| Engine |
Idle |
)
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.
Measurement Method
)
- Disconnect the ignition coil connector, and connect the special tool Test harness (MB991658) 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 probe to engine-A/T-ECU terminal No. 31. (When checking the number 1 cylinder.)
- Connect the oscilloscope probe to engine-A/T-ECU terminal No. 32. (When checking the number 2 cylinder.)
- Connect the oscilloscope probe to engine-A/T-ECU terminal No. 35. (When checking the number 3 cylinder.)
- Connect the oscilloscope probe to engine-A/T-ECU terminal No. 52. (When checking the number 4 cylinder.)
Standard Wave Pattern
| Function |
Special patterns |
|---|---|
| Pattern height |
Low |
| Pattern selector |
Display |
| Engine |
Approximately. 1,200 r/min |
)
Wave Pattern Observation Points
Point: When the engine speed increases, verify that the power transistor control signal
(ignition timing) advances.Examples of Abnormal Wave Patterns
)
- Example
Wave pattern during engine cranking
- Open-circuit in ignition primary circuit
Cause of problem
- Top-right part of the build-up section cannot be seen, and voltage value is approximately 2 V too low.
Wave pattern characteristics
Measurement Method
)
- Disconnect the EGR valve connector, and connect the special tool test harness (MB991658) in between.
- Connect the oscilloscope probe to the EGR valve-side connector terminal 1, terminal 3, terminal 4 and terminal 6 respectively.
Alternate Method (Test Harness not Available)
- Connect the oscilloscope probe to engine-A/T-ECU terminal No. 3, connection terminal No. 12, connection terminal No. 19, and connection terminal No. 26 respectively.
Standard Wave Pattern
| Function |
Special patterns |
|---|---|
| Pattern height |
High |
| Pattern selector |
Display |
| Engine |
Ignition switch: OFF →
ON |
)
Wave pattern Observation Points
Check that the standard wave pattern appears when the EGR control servo 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 Patterns
)
- Example 1
- Sensor interface malfunction. (Motor is not operating)
Cause of problem
- Induced electromotive force from the motor turning dose not appear.
Wave pattern characteristics
)
- Example 2
- Open circuit in the line between the EGR valve and the engine-A/T-ECU.
Cause of problem
- Current is not supplied to the motor coil on the open circuit side. (Voltage dose not drop to 0 V.)
- Furthermore, the induced electromotive force waveform at the normal side is slightly different from the normal waveform.
Wave pattern characteristics