Oscilloscope Patterns and Waveforms

WAVE PATTERN INSPECTION USING AN ANALYZER MEASUREMENT METHOD
1. Disconnect the injector connector and connect the special tool (test harness: MB991348) in between. (Both the terminal on the engine control module side and the terminal on the power supply side should be connected.)
2. Connect the analyzer special patterns pickup to the test harness clip on the engine control module side.





ALTERNATE METHOD (test harness not available)
1. Connect the analyzer special patterns pickup to ECM terminal No. 1, No. 2, No. 14 or No. 15.

Observation conditions

Function Special patterns

Pattern height Variable
Variable knob Adjust while viewing the wave pattern
Pattern selector Display
Engine RPM's Idle

Wave pattern observation points
Point A: Height of injector coil induced voltage

Contrast with Probable cause
standard wave pattern

Injector coil induced voltage Short in the injector solenoid
is low or doesn't
appear at all.





Point B: Injector drive time

^ The injector drive time will be synchronized with the scan tool 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.