P0505

DIAGNOSTIC TROUBLE CODE P0505
Idle air control valve, malfunctioning

Fault symptom
Low, high or unsteady idling speed. Idling speed sensitive to changes in load.

Conditions.
- the throttle position sensor indicates idling
- engine speed is higher than 1200 rpm or lower than 700 rpm
- normal idling speed cannot be achieved

DIAGNOSTIC PROCEDURE

1. Checking for air leakage
Check whether air leakage occurs as follows:
Start the engine and run it at idling speed. Restrict the flow of air through the idle air control valve by using a pair of pliers to squeeze the air hose.

The idling speed should drop sharply.

If idling speed drops, continue with point 2.

If idling speed does not drop, continue fault diagnosis by carrying out the following checks:
- air leakage (after the throttle)
- maladjusted throttle
- faulty brake servo
- EVAP canister purge valve jammed open







2. Checking the operation of the idle air control valve
Switch off the engine.

Unplug the idle air control valve connector. Connect the test lamp to pins 1 and 2 of the idle air control valve connector. Ignition switch in the ON position.

Connect the Scan Tool.
Select "ACTIVATE".
Select "AC VALVE".

The test lamp should light up for 10 seconds.


If the test lamp lights up, continue with point 5.

If the test lamp does not light up, continue with point 3.

3. Checking the wiring harness
Check for continuity between the idle air control valve and the control module.

Take a reading of the resistance across pin 1 of the idle air control valve connector and a good ground on the engine.

Turn the ignition switch to the ON position and then back to the OFF position. Check the resistance.

The resistance should be 5-15 ohms.

If the reading is OK, the fault has been traced to the lead between pin 2 of the connector and crimped connection J67. Investigate the cause and rectify the fault.

If the reading is not OK, continue with point 4.





4. Checking the wiring harness
Check the lead between pin 1 of the connector and pin 49 of the control module for shorting and continuity.

If the lead is OK, continue with point 7.

If the lead is not OK, rectify the fault.

5. Checking the resistance of the idle air control valve
Take a reading of the resistance across pins 1 and 2 of the IAC valve connector.

Nominal resistance is 7.7 ±1 ohms.

If the reading is OK, continue with point 6.

If the reading is not OK, change the idle air control valve.








6. Checking the operation of the control slide
Disconnect the IAC valve's air hoses.
Plug in the AC valve's electrical connectors.
Select "ACTIVATE".
Select "IAC VALVE".

Activation takes place for 10 seconds. If longer activation is required the command must be repeated.

Check visually that the slide turns without displaying any tendency to bind.

If the slide is OK, continue with point 7.

If the slide binds or jams, change the idle air control valve.

7. Final check
Clear the diagnostic trouble code, drive the car on test and check whether the trouble code is generated afresh.

If the DTC is generated again, refer to Before Replacing A Control Module.

If the DTC is not generated again, the action taken to rectify the fault was correct, otherwise the fault is of intermittent nature.