Page text (OCR transcript)
EG–586
ENGINE – 2JZ–GTE ENGINE TROUBLESHOOTING
IAC Valve Circuit
CIRCUIT DESCRIPTION
The IAC valve is situated on the intake air chamber Intake air bypassing the throttle valve is directed to the IAC valve through a passage.
A step motor is built into the IAC valve. It consists of 4 coils, a magnetic rotor, valve shaft and a valve.
When the current flows to the coils due to signals from the ECM, the rotor turns and moves the valve shaft forward or backward, changing the clearance between the valve and the valve seat.
In this way the intake air volume bypassing the throttle valve is regulated, controlling the engine speed.
There are 125 possible positions to which the valve can be opened.
Throttle Body
Intake
Air
Chamber
From
Air
Flow
Meter
Valve
Throttle
Valve
Coils
To
Cylinder Head
Rotor
Valve Shaft
FI6973
Reference INSPECTION USING OSCILLOSCOPE
A/C Switch OFF → ON
(IAC Valve open)
ISC1
ISC2
ISC3
ISC4
20 V/Div.
10 msec./Division
• With the engine idling measure wave forms between terminals ISC1, ISC2, ISC3, ISC4 and E01 of engine control module when A/C switch ON or OFF.
HINT:
The correct waveforms are as shown.
A/C Switch ON → OFF
(IAC Valve close)
ISC1
ISC2
ISC3
ISC4
20 V/Div.
10 msec./Division
FI6536
FI6537
