I'm assuming that you have idle high in the engine, and IAC fault code.
DIAGNOSTIC TROUBLE CODE (DTC) 0505 IDLE AIR CONTROL VALVE (IACV) CIRCUIT FAULT
Know Your Circuit:
* In order to regulate the air entering into the engine, the Engine Control Module (ECM) uses an Idle Air Control (IAC) Valve.
* To raise the idle rpm, the ECM handles the pintle inside the IAC valve away from the throttle body seat.
* This enables additional air to bypass through the throttle blade.
* To lower the rpm the ECM controls the pintle towards the throttle body seat.
* This successfully reduces the amount of air bypassing the throttle blade.
* A scan tool will note the IAC valve pintle position.
* The greater the count, the greater air is allowed to bypass the throttle blade.
* This DTC ensures whether a low idle condition exists as defined as 100 rpm below the desired idle rpm.
Pre -requisites For Setting the DTC:
· No intrusive tests are active.
· DTC(s) P0106, P0107, P0108, P0112, P0113, P0117, P0118, P0122, P0123, P0131, P0132, P0133, P1133, P1134, P0171, P1171, P0172, P0201, P0202, P0203, P0204, P0300, P0336, P0337, P0341, P0342, P0351, P0352, P0402, P0404, P1404, P0405, P0406, P0443, and P0502 are not set.
· Engine is running > 60 seconds.
· Barometric Pressure (BARO) is > 72 k Pa (10.4 psi).
· Engine Coolant Temperature (ECT) is > 60°C (140°F).
· Ignition voltage ranges between 11 and 16 volts.
· The Intake Air Temperature (IAT) is > -20°C (-4°F).
· Manifold Absolute Pressure is less than 60 k Pa (8.7 psi).
· IAC valve is fully opened.
· All of the above must be met for more than 5 seconds.
* Probe the IAC valve electrical connection for proper mating.
* Examine the wiring harness for damage.
* See whether the throttle stop screw shows signs of distortion.
* Also inspect the throttle linkage for signs of binding or excessive wear and tear.
* The following conditions may be created by a slow or unsteady idle:
1) Fuel system very high or low.
2) Foreign material in the throttle body or in the induction system bore
3) A leaking or restricted intake manifold.
4) Excessive engine overloading. Check for seized pulleys, pumps, or motors on the accessory drive
5) Excess engine oil.
SUMMARY OF THE STEPS TO BE TAKEN
DTC P0505 Idle Air Control Valve (IACV) Circuit Fault
Hope this help.