Toyota Corolla (E120) 2002–2008 Repair Manual / Diagnostics / Sfi system / Idle air control System/ Circuit / Circuit description
Toyota Corolla (E120): Circuit description
The rotary solenoid type idle air control (iac) valve is located under the throttle body and intake air bypassing the throttle valve flows into the iac valve through the passage.
In this way the intake air volume bypassing the throttle valve is regulated, controls the engine speed.
The ecm operates the iac valve only to perform idle–up and provide feedback for the target idling speed.
Monitor description
The idle speeds are determined depending on the volume of air that passes through the iac valve. When the volume is large, the idle speed becomes higher. When the volume is small, the idle speed becomes lower.
The iac valve controls the air volume that bypasses the throttle valve. The engine control module (ecm) sends duty signals to the iac valve and drives the iac valve stepper motor to determine the air volume that bypasses the throttle valve.
Although the ecm regulates the idle engine rpm with the feedback control in several vehicle stopped, actual idle rpm does not reach the targeted rpm and a learned valve angle of the idle air control (iac) remains at the maximum or remains at the minimum, the ecm determines to detect malfunction in the iac system.
Example: if the rpm difference between the targeted and actual idle engine rpms exceeds 200 rpm (*1) with the vehicle stopped in an idle, and this occurs 5 times, or if the learned value angle of the iac remains at its maximum or minimum angle for 5 seconds, p505 is detected.
P0511 is detected as an open/short circuit in the iac if the rate of duty signal input to the iac valve has stuck at 0 or 100 %.
*1: Threshold rpm is varied by an engine load.
Monitor strategy
Typical enabling condition
Typical malfunction thresholds
Component operating range
Wiring diagram
Other materials:
Changing the engine switch positions
1 “LOCK”
The steering wheel is locked and the key can be removed. (Vehicles with an automatic
transmission or continuously variable transmission: The key can be removed only
when the shift lever is in P.) 2 “ACC”
Some electrical components such as the audio system can be used.
3 “ON ...
Replacement
1. Drain brake fluid
Notice:
wash the brake fluid off immediately if it comes into contact with any painted
surface.
2. Remove front wheel rh
3. Remove front fender liner rh
4. Remove brake actuator with bracket
turn the latch of the actuator connector to disconnect the
connector. ...
Monitor description
While the engine is being cranked, the battery positive voltage is applied to
terminal sta of the ecm.
If the ecm detects the starter control signal (sta) while the vehicle is
driving, it will conclude that there is
a fault in the starter control circuit. The ecm will turn on the mil and a d ...