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.

When is DTC set?

When will DTC clear?

1) The Malfunction Indicator Lamp (MIL) will glow.

 

1) The MIL will switch off after four successive ignition cycles in which the diagnostic runs flawlessly.

 

2) The ECM will note operating conditions at the time the diagnostic fails.

2) A history DTC will clear after 40 repetitive warm up cycles without a fault.

 

3) This information will be kept in the Freeze Frame and failure records will buffer.

 

3) Scan tools will help to rid the DTCs.

 

4) A history DTC is stored.

 

 

 4) Disconnecting the ECM battery feed for more than 10 seconds

 

 

Diagnostic Tools

  • 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

 

 

Step

Process

Value(s)

R     E     S      

U      L     T

1

Do the EOBD System Check

Task Done?

-

IF YES THEN

 

 

 

Follow Step 2

IF NO THEN

Follow "On-Board Diagnostic System Check"

2

1)  Connect a scan tool to the Data Link Connector (DLC).

1)       Run the engine at idle speed.

2)       Run transmission in park or neutral and set the parking brake.

3)       Switch off A/C.

4)       Shift the Idle Air Control (IAC) valve up and down within the stated value using a scan tool.

Do you see the rpm change smoothly when commanded by the scan tool?

900-1200 rpm

IF YES THEN

 

Follow Step 3

IF NO THEN

 

Follow Step 5

3

  1. Switch the ignition OFF.
  2. Remove the IAC valve connector.
  3. Measure and note the resistance between terminal C and D of the IAC valve.
  4. Now measure and note the resistance between terminal B and A of the IAC valve.

Do you see that the value of the resistance is within the specified value?

40-80 ohms

 IF YES THEN

 

 

 

 

 

Follow Step 4

IF NO THEN

 

 

 

 

 

Follow Step 13

4

  1. Count the resistance between terminal D and B of the IAC valve.
  2. Observe the resistance between terminal C and A of the IAC valve.

Do you see the resistance equal to the specified value?

infinite

IF YES THEN

Follow Step 15

IF NO THEN

Follow Step 13

5

  1. Again turn the ignition OFF.
  2. Detach the IAC valve connector.
  3. Now turn the ignition ON.
  4. Keeping the test light connected to ground, check the IAC connector terminals.

Does the test light on terminal D blink?

-

IF YES THEN

Follow Step 6

IF NO THEN

Follow Step 7

6

Examine the IAC connector terminals keeping the test light connected to B+.

 

Do you see the test light glowing at terminal D?

-

IF YES THEN

 

Follow Step 8

IF NO

THEN

 

Follow Step 9

7

Look for an open or short to ground in both the IAC circuits and mend as necessary.

 

Task Done?

-

IF YES THEN

 

Follow Step 15

IF NO THEN

 

Follow Step 10

8

  1. Now idle the engine.
  2. Placing a test light to ground, test the IAC connector terminals.

Does the test light glow On and OFF simultaneously for all terminals?

-

IF YES THEN

 

Follow Step 11

IF NO THEN

 

Follow Step 12

9

Look for an open or short to ground in both the IAC circuits and mend as necessary.

 

Task Done?

-

IF YES THEN

 

Follow Step 15

IF NO

THEN

 

Follow Step 10

10

See whether  the Engine control Module (ECM) is poorly connected and repair accordingly.

 

Work done?

-

IF YES THEN

 

Follow Step 15

IF NO THEN

 

Follow Step 14

11

Inspect the IAC valve passages and repair if the need be.

 

Task over?

-

IF YES THEN

 

Follow Step 15

IF NO THEN

 

Follow Step 13

12

 Probe the test light.

 

Do you see the test light ON throughout for the terminals that did not blink?

-

IF YES THEN

 

Follow Step 9

IF NO THEN

 

Follow Step 7

13

  1. Turn the ignition OFF.
  2. Change the IAC valve.

Task Done?

-

IF YES THEN

 

Follow Step 15

-

14

  1. Turn the ignition OFF.
  2. Replace the ECM.

Work Done?

-

IF YES THEN

 

Follow Step 15

-

15

  1. Clear The DTC
  2. Start the engine and idle at normal operating temperature.
  3. Run the vehicle within the pre-requisites for setting this DTC as given in the supporting text.

Does the scan tool indicate that this diagnostic has been run and passed?

-

IF YES THEN

 

 

 

Follow Step 16

IF NO  THEN

 

 

 

Follow Step 2

16

Check if any additional DTCs are set.

Do you see any undiagnosed DTC set?

-

IF YES THEN

 

Follow Applicable DTC Table

The System of your car is perfect.