Oscilloscope Patterns and Waveforms

MEASUREMENT METHOD
1. Disconnect the injector connector and connect the special tool (test harness: MB991 348) 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 (TEAT HARNESS NOT AVAILABLE)
1. Connect the analyzer special patterns pickup to ECM terminal 1 to analyze the No.1 cylinder, connection terminal 2 to analyze the No.3 cylinder, connection terminal 14 to analyze the No.2 cylinder and connection terminal 15 to analyze the No.4 respectively.





OBSERVATION CONDITIONS

Function Special patterns

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

WAVE PATTERN OBSERVATION POINTS

Point A: Height of injector coil induced voltage

Contrast with standard wave pattern Probable cause

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





Point B: Injector drive time

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