Diagnostic Aids

WARNING: This page is about a different car, the 2003 Pontiac Vibe. However, it is still accessible from the selected car via links, so may be relevant.

With engine idling at normal operating temperature and all accessories OFF, monitor the following parameters on scan tool for correct operation:

IAC Motor Command - 25-45 percent.
Electrical load - No.
Commanded A/C - OFF.

Scan tool can be used to isolate the cause of an intermittent DTC P0505. Engine idle speed can be controlled sing the scan tool. Operate IAC valve using scan tool while checking for a smooth increase and decrease in engine speed. If engine speed can be controlled, IAC system is functioning normally. Check for the following conditions:

Any blockage of air intake system.
Any blockage of IAC passage.
Excessive deposits on throttle plate or throttle bore.
Any large vacuum leaks.

An intermittent malfunction may be caused by a fault in IAC sensor electrical circuit. Check wiring harness and related components for an intermittent condition. See INTERMITTENTS in TROUBLE SHOOTING - NO CODES - 1.8L VIBE article. Repair any electrical circuit faults found. Information included in freeze frame data can be useful in determining vehicle operating conditions when DTC first set. If DTC P0505 does not reset, but a driveability symptom still exists, diagnose by symptom. See TROUBLE SHOOTING - NO CODES - 1.8L VIBE article.