Colt Vista FWD L4-1795cc 1.8L SOHC (1994)
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 analyzer special patterns pick up to ECM terminals 1,2, 14, 15.
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 analyzer special patterns pick up to ECM terminals 1,2, 14, 15.
Explanation of Wave Pattern
Normally the power voltage is displayed, but when an injector drive "ON" signal is output by the engine control module. voltage drops to around
OV for the duration of this "ON" signal only. When the drive signal from the engine control module becomes "OFF", a voltage peak appears due
to the coil back electromotive force. and after this, it returns to power voltage.
Injector drive time:
The fuel injection time computed by the engine control module from the output values from each sensor such as the volume
air flow sensor Injector drive time = effective injection time + ineffective injection time
(Ineffective injection time:compensates for retarded injector operation due to the drop in power source voltage.) Solenoid
back electromotive force: When the injector drive signal from the engine control module is turned OFF, a back
electromagnetic force is generated in the injector coil (Approximately 65-75V).
Power source voltage:
When there is no "ON" signal from the engine control module, power supply voltage is displayed. When this power supply
voltage is low, the ineffective injection time is long and injector drive time also is long.
Wave Pattern Observation Points
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The injector drive time will be synchronized with the scan tool display.
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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.
