Troubleshooting

DTC P0505 Idle Air Control System

CIRCUIT DESCRIPTION

DTC Detection Condition:

The rotary solenoid type of the idle speed control (ISC) valve is located under the throttle body and intake air bypassing the throttle valve flows to the idle speed control (ISC) valve through the passage.

In this way the intake air volume bypassing the throttle valve is regulated, and controls the engine speed.

The ECM operates the idle speed control (ISC) valve only to perform idle-up and provide feedback for the target idling speed.

MONITOR DESCRIPTION

Monitor Strategy:

Typical Enabling Conditions:

Typical Malfunction Thresholds:

Component Operating Range:

The idle speed is determined depending on the volume of air that passes through the ISC valve. As the volume is large, the idle speed becomes higher. As the volume is small, the idle speed becomes lower. The ISC valve controls the volume of air that bypasses the throttle valve. The ECM (engine control module) sends duty signals to the ISC valve and drives the ISC valve to determine the volume of air that bypasses the throttle valve.

Although the ECM regulates the idle engine RPM with the feedback control, actual idle RPM dose not reach the targeted RPM and a learned valve angle of the ISC (idle speed control) remains at the maximum or remains at the minimum, the ECM determines the condition as a malfunction in the ISC system.

If the rate of duty signal input to the ISC valve is stuck to 0 or 100%, the ECM interprets it as an open/short circuit in the ISC valve and sets a DTC.

Example:
Difference between the target RPM and actual RPM exceeds 200 rpm (*1) with the vehicle stopped in idle, occurs 5 times.
*1: The threshold varies by an engine load.

Wiring Diagram:

INSPECTION PROCEDURE

Step 1 - 3:

Step 4 - 6:

Step 7 - 8:

Step 9:

When using hand-held tester

Step 1 - 3:

Step 4 - 5:

Step 6 - 7:

When not using hand-held tester

HINT: Read freeze frame data using the hand-held tester or the OBD II scan tool. Freeze frame data records the engine conditions when a malfunction is detected. When troubleshooting, it is useful to determine whether the vehicle was running or stopped, the engine was warmed up or not, the air-fuel ratio was lean or rich, etc. at the time the malfunction occurred.

CHECK FOR INTERMITTENT PROBLEMS

Hand-held tester only:
By putting the vehicle's ECM in the check mode, the 1 trip detection logic is possible instead of the 2 trip detection logic, and the sensitivity to detect faults is increased. This makes it easier to detect intermittent problems.

a. Clear the DTCs.
b. Set the check mode.
c. Perform a simulation test.
d. Check the connector and terminal.
e. Wiggle the harness and connector.