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Monitor Description

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 sensor 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. If the actual idle RPM varies more than a specified amount or a learned value of the idle speed control remains at the maximum or minimum five times or more during a trip, the ECM concludes that there is a problem in the idle speed control ECM function. The ECM will turn on the MIL and a DTC will be set.

Example:

If the actual idle RPM varies from the target idle RPM by more than 200 (*1) rpm five times during a drive cycle, the ECM will turn on the MIL and a DTC will be set.

HINT:

*1: RPM threshold varies depending on engine loads.

Fig 1: Engine RPM And Time Graph
G05188849Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
DTC TROUBLE DETECTION CONDITION CHART

DTC No. DTC Detection Condition Trouble Area
P0505 Idle speed continues to vary greatly from target speed (1 trip detection logic)
  • Electronic throttle control system
  • Air induction system
  • PCV valve and hose
  • ECM