Component Tests and General Diagnostics
INSPECTION PROCEDURE USING AN OSCILLOSCOPEVOLUME AIRFLOW SENSOR
Required Special Tool:
- MB991709: Test Harness
Measurement Method
1. Disconnect the volume airflow sensor connector and connect the test harness special tool (MB991709) in between. (All terminals should be connected.)
2. Connect the oscilloscope probe to volume airflow sensor connector terminal 3.
Alternate method (Test harness not available)
1. Connect the oscilloscope probe to ECM terminal 61.
1. Connect the oscilloscope probe to PCM terminal 65.
Standard Wave Pattern
Wave Pattern Observation Points
1. 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. An ignition leak will distort the wave pattern temporarily, even if the volume airflow sensor is normal.
CAMSHAFT POSITION SENSOR AND CRANKSHAFT POSITION SENSOR
Required Special Tools:
- MB991348: Test Harness
- MD998478: Test Harness
Measurement Method
1. Disconnect the camshaft position sensor connector and connect the test harness special tool (MB991348) in between. (All terminals should be connected.)
2. Connect the oscilloscope probe to camshaft position sensor connector terminal 5.
3. Disconnect the crankshaft position sensor connector and connect the test harness special tool (MD998478) in between.
4. Connect the oscilloscope probe to crankshaft position sensor connector terminal 2 (black clip of special tool).
Alternate method (Test harness not available)
1. Connect the oscilloscope probe to ECM terminal 50. (Check the camshaft position sensor signal wave pattern.)
2. Connect the oscilloscope probe to ECM terminal 43. (Check the crankshaft position sensor signal wave pattern.)
1. Connect the oscilloscope probe to PCM terminal 56. (Check the camshaft position sensor signal wave pattern.)
2. Connect the oscilloscope probe to PCM terminal 45. (Check the crankshaft position sensor signal wave pattern.)
Standard wave pattern
Wave Pattern Observation Points
1. Check that cycle time T becomes shorter when the engine speed 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
Loose timing belt.
Abnormality in sensor disc.
- Wave pattern characteristics
Wave pattern is displaced to the left or right.
INJECTOR
Required Special Tools:
- MB991348: Test Harness
- MD998464: Test Harness
Measurement Method
1. Disconnect the injector intermediate connector and connect the test harness special tool (MD998464) in between.
2. Connect the oscilloscope probe to each injector intermediate connector terminal to analyze each cylinder:
- Terminal 2 (black clip of special tool) for the number 1 cylinder
- Terminal 3 (blue clip) for the number 3 cylinder
- Terminal 4 (white clip) for the number 5 cylinder
1. Disconnect the injector connector and connect the test harness special tool (MB991348) in between. (All terminals should be connected.)
2. Connect the oscilloscope probe to injector connector terminal 2.
Alternate method (Test harness not available)
1. Connect the oscilloscope probe to ECM
2. Connect the oscilloscope probe to ECM
3. Connect the oscilloscope probe to ECM
4. Connect the oscilloscope probe to ECM
5. Connect the oscilloscope probe to ECM
6. Connect the oscilloscope probe to ECM
Standard Wave Pattern
Wave Pattern Observation Points
Point A: Height of injector coil induced voltage.
Point B: Injector drive time
1. The injector drive time should be synchronized with the scan tool tester display.
2. 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.
IDLE AIR CONTROL MOTOR (STEPPER MOTOR)
Required Special Tool:
- MB991709: Test Harness
Measurement Method
1. Disconnect the idle air control motor connector and connect the test harness special tool (MB991709) in between. (All terminals should be connected.)
2. Connect the oscilloscope probe to the idle air control motor connector terminal 1, terminal 3, terminal 4 and terminal 6, respectively.
Alternate method (Test harness not available)
1. Connect the oscilloscope probe to ECM
Standard Wave Pattern
Wave Pattern Observation Points
1. Check that the standard wave pattern appears when the idle air control motor 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 idle air control motor 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 Tool:
- MB991348: Test Harness Set
Measurement Method
1. Disconnect the connector and connect test harness special tool, (MB991348), in between. (All terminals should be connected.)
2. Connect the oscilloscope probe to ignition coil connector terminal 3.
Alternate method (Test harness not available)
1. Connect the oscilloscope probe to ECM
Standard Wave Pattern
Wave Pattern Observation Points
Point: Condition of wave pattern build-up section and maximum voltage (Refer to abnormal wave pattern examples 1 and 2).
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 volts too low.
Example 2 (Wave pattern during engine cranking)
- Cause of problem
Malfunction in ignition power transistor
- Wave pattern characteristics
Power voltage results when the ignition power transistor is ON.