DTC P0505: Idle Air Control (IAC) System Malfunction
- Ensure idle speed and IAC duty are within specifications. See IDLE SPEED in ON-VEHICLE ADJUSTMENTS article. If idle speed and IAC duty are within specifications, check for an intermittent problem. See TROUBLE SHOOTING - NO CODES article. Then if no problems were found, replace PCM and retest system. If idle speed does not stay within specification, go to next step.
- Check idle air control valve operation. See IDLE AIR CONTROL (IAC) VALVE under IDLE CONTROL SYSTEM in SYSTEM & COMPONENT TESTING article. If idle air control valve operates as specified, go to step 5 . If operation is not as specified, go to next step.
- Turn ignition off. Disconnect PCM harness connectors. Using DVOM, check resistance between PCM harness connector terminals C51-2-3 (Light Green/Black wire) and C51-2-12 (Purple/Black wire). Also check resistance between PCM harness connector terminals C51-2-10 (Purple/Yellow wire) and C51-2-11 (Gray/Blue wire). Resistance on both circuits should be between 70-86 ohms. If resistance readings are as specified, go to next step. If resistance readings are not as specified, Check for open or short circuits on appropriate wire(s). If wiring and connectors are okay, replace IAC valve.
- Reconnect PCM harness connectors. Disconnect IAC valve harness connector. Turn ignition on and check for voltage at IAC valve harness connector terminals No. 2 and 5 (Blue/Black wires). If voltage readings are between 10-14 volts, either IAC valve or PCM is defective. Replace as necessary. If voltage is not as specified, repair open circuit in Blue/Black wire between IAC valve and main relay.
- If idle speed in step 2 was higher than specifications, check for intake leak at intake manifold, throttle body, PCV valve or EVAP canister purge control system. If idle speed was lower than specifications, check for intake leak between throttle body and MAF sensor. Also see ROUGH OR UNSTABLE IDLE under SYMPTOMS in TROUBLE SHOOTING - NO CODES article.