P0506

IDLE AIR CONTROL VALVE





Symptom Of Fault.
Low, high or hunting idle speed.
Idle speed sensitive to load changes.

Conditions.
^ The speed of the car has exceeded 12 mph (20 km/h) in this driving cycle.
^ The car is stationary.
^ Engine coolant temperature > 60°C (> 140°F)
^ Throttle position sensor indicates idling speed.
^ Engine speed is above 1200 rpm or below 700 rpm
^ Normal idling speed cannot be achieved

Diagnostic Help.
Operation of the idle air control valve can be checked with the ISAT scan tool.
- To ascertain the current degree of opening:
- Select "READ FUNCTIONS".
- Select "IAC VALVE"
- To activate the valve:
- Select "ACTIVATE".
- Select "IAC VALVE"
- The valve will be activated for 10 sec.





Diagnostic Procedure.
1. Check for air leakage
- Check whether air leakage occurs, as follows:
- Start the engine and run it at idling speed.
- Constrict the flow of air through the idle air control valve by pinching off the air hose using a pair of pliers.
Idling speed should drop drastically.

Has idling speed dropped?
YES:
^ Continue with point 2.
NO:
^ Continue fault diagnosis by carrying out the following checks: 9 air leakage (after throttle)
^ poorly adjusted throttle
^ defective brake servo
^ purge valve fastened in open position Rectify as necessary and then continue with point 4.




2. Check the idle air control valve's power supply
- Switch off the engine.
- Unplug the idle air control valve's 2-pin connector.
- Start the engine and run it at idling speed.
- Connect the test lamp to pin 2 of the female connector and a good grounding point on the engine.
The test lamp should light up.

Is the test lamp on?
YES:
^ Continue with point 3.
NO:
^ Repair or replace the lead between pin 2 of the connector and crimped connection J67.
Then continue with point 4.





3. Check the lead between the idle air control valve and the control module
- Switch off the engine.
- Turn the ignition switch to the ON position and then back to the OFF position.
- Connect the test lamp to pin 1 of the female connector and battery positive (B+). The test lamp should light up.
- Remove fuse 23. The test lamp should now shine weakly or go out completely.

Has the test lamp gone out or nearly so?
YES
^ Change the idle air control valve and continue with point 4.
NO:
^ Check the lead between pin 1 of the connector and pin 49 of the control module for continuity and shorting. Rectify if necessary.
Then continue with point 4.





4. Final check:
- Clear the diagnostic trouble code.
- Perform a driving cycle:
^ Drive the car at varying engine loads and rpm until the coolant temperature rises above 60°C (140°F), but for at least 1 minute if this temperature is reached earlier.
^ Car speed should exceed 12 mph (20 km/h) at some time during the driving cycle.
^ Stop the car, apply the hand brake and run the engine at idling speed.
^ Switch off the A/C and all electrical equipment. If the car has automatic transmission, select position P.
Allow the engine to stabilize its idling speed for 10 sec.
^ Switch on the A/C and all electrical equipment. If the car has automatic transmission, select position D. Allow the engine to stabilize its idling speed for 10 sec.
- Evaluation of driving cycle: Check whether the diagnostic trouble code has recurred.

Has the diagnostic trouble code recurred?
YES:
^ Proceed at "Before Replacing a Control Module". Component Tests and General Diagnostics
NO:
^ The remedial measure taken was correct.