Toyota Celica 2005 Repair Manual page 456

MONITOR DESCRIPTION
Idle engine RPM
The idle speed is controlled by the Electronic Throttle Control System (ETCS).
The ETCS is composed of the throttle motor, which operates the throttle valve, and the throttle position sen-
sor, which detects the opening angle of the throttle valve.
The ECM controls the throttle motor to provide the proper throttle valve opening angle to obtain the target
idle speed.
The ECM regulates the idle speed by opening and closing the throttle valve using the ETCS. The ECM con-
cludes that the idle speed control ECM function is malfunctioning if: 1) the actual idle RPM varies more than
the specified amount, or 2) a learning value of the idle speed control remains at the maximum or minimum
five times or more during a driving cycle. The ECM will turn on the MIL and set a DTC.
Example:
If the RPM difference between the target and actual idle engine RPM exceeds 200 rpm (*1) with the vehicle
stopped with idling, and this occurs 5 times, or if the learning value angle of the IAC remains at its maximum
or minimum angle for 5 seconds, P0505 is detected.
P0511 is detected as an open or short in the IAC circuit if the rate of duty signal input to the IAC valve has
stuck at 0 or 100%.
HINT:
*1: RPM threshold varies with engine load.
2005 CELICA (RM1131U)
DIAGNOSTICS −
Target RPM
Actual idle RPM
Time
455
ENGINE (1ZZ−FE)
Large
Learning Value
of ISC
0
Small
DI−257
Maximum
Minimum
Time
A20597