Oscilloscope Patterns and Waveforms

Wave Pattern Inspection Using an Analyzer
Measurement method
(1) Disconnect the volume air flow sensor connector, and connect the special tool (test harness: MB991348) in between. (All terminals should be connected.)
(2) Connect the analyzer special patterns pickup to terminal.
(3) of the volume air flow sensor connector.

Alternative method (when test harness is not available)
Connect the analyzer special patterns pickup to ECM terminal (90).




Standard wave pattern Observation Conditions




Standard wave pattern




Observation conditions (Pattern changes with engine speed changes)

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
Malfunction of sensor interface

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 it the volume air flow sensor is normal.