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Makes 🢒 Pontiac 🢒 2006 🢒 Vibe - AWD 🢒 Restraints 🢒 SIR 🢒 DTC P0505

DTC P0505 AWD

Circuit Description

The DTC P0505 Idle Control System diagnostic observes engine speed in order to monitor the operation of the IAC valve. The powertrain control module (PCM) controls engine idle speed with the idle air control valve. To increase the idle speed, the PCM pulse width modulates the OPEN solenoid within the IAC valve. This action turns a cylinder within the IAC valve, allowing air to bypass the throttle plate. The PCM regulates fast idle speed via the IAC valve by increasing the opening of the air bypass port. The PCM regulates slow idle speed via the IAC valve by decreasing the opening of the air bypass port.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC P0505 Idle Control System

Conditions for Running the DTC
    • DTCs P0011, P0012, P0031, P0032, P0100, P0101, P0102, P0103, P0115, P0117, P0118, P0120, P0121, P0122, P0123, P0125, P0130, P0133, P0134, P0171, P0172, P0300, P0301-P0304, P0335, P0340, P0341, P0351-P0354, P0385, P0500, P0850 are not set.
    • The battery voltage is more than 11 volts.
    • The engine coolant temperature is at least 75°C (167°F).
    • The engine is running at idle conditions.
    • Vehicle speed is less than 3 km/h (1.8 mph).
    • When the above conditions have been met, DTC P0505 runs once per drive cycle for Condition 1 and Condition 2.
    • When the above conditions have been met, DTC P0505 runs continuously for Condition 3.

Conditions for Setting the DTC
    • Condition 1--The observed engine speed at idle is less than the expected engine speed by 100 RPM or more.
    • Condition 2--The observed engine speed at idle is more than the expected engine speed by 150 RPM or more.
        Either of the above conditions has occurred 5 times or more this drive cycle.
    • Condition 3--The IAC motor duty cycle is less than 10 percent or more than 90 percent for 10 seconds.

Action Taken When the DTC Sets
    • The PCM illuminates the malfunction indicator lamp (MIL) after 2 consecutive ignition cycles in which the diagnostic runs with an active Condition 1 or Condition 2 fault.
    • The PCM illuminates the MIL immediately with an active Condition 3 fault.
    • The PCM stores the conditions which were present when the DTC set as Freeze Frame data.

Conditions for Clearing the MIL/DTC
    • The PCM turns OFF the MIL on the third consecutive trip cycle during which the diagnostic has been run and the fault condition is no longer present.
    • The DTC clears after 40 consecutive warm-up cycles have occurred without a fault.
    • A DTC can be cleared by using the scan tool Clear DTC Information function.

Diagnostic Aids
    • With the engine idling at a normal operating temperature and all accessories OFF, monitor the following parameters on the scan tool:
       - The IAC Motor Command--27 to 43 percent
       - Engine speed--650 to 750 RPM
       - Electrical load--No
       - Commanded A/C--OFF
       - If any of the above parameters is outside of the typical value as indicated, inspect for the cause and repair as necessary.
    • Inspect the carpet or floor mat for interfering with the free movement of the accelerator pedal.
    • The scan tool can be used to isolate the cause of an intermittent DTC P0505. Engine idle speed can be controlled with the scan tool. Operate the IAC valve with the scan tool while checking for a smooth increase and decrease in engine speed. If engine speed can be controlled, the IAC system is functioning normally.
    • Check for the following conditions:
       - Any blockage of the air intake system
       - Any blockage of the IAC passage
       - Excessive deposits on the throttle plate or the throttle bore
       - Any large vacuum leaks
    • An intermittent malfunction may be caused by a fault in the IAC sensor electrical circuit. Inspect the wiring harness and the components for an intermittent condition. Refer to Intermittent Conditions .
    • The information included in the Freeze Frame data can be useful in determining the vehicle operating conditions when the DTC first set.
    • If the DTC P0505 does not reset, but a driveability symptom still exists, refer to Symptoms - Engine Controls .

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. This step simulates the pulse width modulated (PWM) signal supplied to the IAC valve by the PCM by rapidly grounding and un-grounding terminal 1 of the IAC valve.

    2.

  2. The most likely cause of no power is an open circuit condition between the IAC valve connector terminal 2 and the splice. A shorted or inoperative EFI relay circuit will cause a no-start condition.

Step

Action

Yes

No

Schematic Reference: Engine Controls Schematics

Connector End View Reference: Powertrain Control Module Connector End Views or Engine Controls Connector End Views

1

Did you perform the Diagnostic System Check - Vehicle?

Go to Step 2

Go to Diagnostic System Check - Vehicle in Vehicle DTC Information

2
  1. Start and idle the engine until the engine reaches a normal operating temperature.
  2. Using a scan tool, store the Freeze Frame and DTC information.
  3. Turn OFF the ignition and wait 30 seconds.
  4. Turn ON the ignition, with the engine OFF.
  5. Perform the scan tool Clear DTC Information function.
  6. Start and idle the engine.
  7. Wait 60 seconds, then check for stored DTCs.

Does this DTC reset?

Go to Step 4

Go to Step 3

3

Is there an idle quality concern?

Go to Rough, Unstable, or Incorrect Idle and Stalling

Go to Diagnostic Aids

4
  1. Inspect the positive crankcase ventilation (PCV) system for the following conditions:
    2. • Inspect for the correct operation of the PCV system--Refer to Crankcase Ventilation System Inspection/Diagnosis
    • Inspect for the correct PCV valve--Refer to Positive Crankcase Ventilation Valve Replacement
  2. Repair or replace as necessary.

Did you find and correct the condition?

Go to Step 13

Go to Step 5

5
  1. Turn OFF the ignition.
  2. Disconnect the idle air control (IAC) valve electrical connector.
  3. Turn ON the ignition, with the engine OFF.
  4. Using a test lamp connected to ground, probe terminal 2 of the IAC valve connector on the harness side.

Does the test lamp illuminate?

Go to Step 6

Go to Step 9

6

Using a test lamp connected to B+, probe terminal 3 of the IAC valve connector .

Does the test lamp illuminate?

Go to Step 7

Go to Step 10

7

  1. Turn OFF the ignition.
  2. Jump terminal 2 of the IAC valve connector on the harness side to terminal 2 of the IAC valve connector with a fused jumper wire.
  3. Jump terminal 3 of the IAC valve connector on the harness side to terminal 3 of the IAC valve connector with a fused jumper wire.
  4. Connect a fused jumper wire to terminal 1 of the IAC valve--not the harness.
  5. Insulate the terminal 1 jumper from contact to ground.
  6. Start and idle the engine.
  7. With the engine idling, repeatedly touch the terminal 1 jumper to battery ground with a rapid ON-OFF motion.

Does engine speed increase as the terminal 1 jumper is rapidly grounded ON and OFF?

Go to Step 8

Go to Step 11

8
  1. Turn OFF the ignition.
  2. Remove all jumpers.
  3. Disconnect the PCM connector containing the IAC valve open control circuit.
  4. Check terminal 1 of the IAC valve open control circuit for a grounded, open, or shorted to voltage circuit.
  5. Repair the circuit as necessary. Refer to Wiring Repairs in Wiring Systems.

Was a circuit repair made?

Go to Step 13

Go to Step 12

9

  1. Locate the cause of no power to the IAC valve connector. Refer to the Test Description.
  2. Repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Is the action complete?

Go to Step 13

--

10

Repair the open IAC valve ground circuit. Refer to Wiring Repairs in Wiring Systems.

Is the action complete?

Go to Step 13

--

11

Important: The IAC valve seals the coolant passage of the throttle body.

Replace the IAC valve. Refer to Idle Air Control Valve Replacement .

Is the replacement complete?

Go to Step 13

--

12

Replace the powertrain control module (PCM). Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming.

Is the replacement complete?

Go to Step 13

--

13
  1. Use the scan tool in order to clear the DTCs.
  2. Turn OFF the ignition for 30 seconds.
  3. Start the engine.
  4. Operate the vehicle within the Conditions for Running the DTC.

Is DTC P0505 set in Last Test Failed?

Go to Step 2

Go to Step 14

14

With a scan tool, observe the stored information, Capture Info.

Does the scan tool display any DTCs that you have not diagnosed?

Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information

System OK

DTC P0505 FWD

Description

The DTC P0505 Idle Control System diagnostic observes engine speed in order to monitor the operation of the throttle actuator control (TAC) system. The powertrain control module (PCM) uses input from several engine sensors in order to determine the correct engine speed at idle. With the desired idle speed calculated, the PCM determines the correct throttle position (TP) needed to obtain the desired engine speed. The PCM sends the desired throttle position or target value to the throttle actuator control (TAC) module. The TAC module achieves the desired throttle position by commanding the throttle control motor to position the throttle valve at the target value. If necessary, the PCM adjusts the target throttle position in order to achieve the desired engine idle speed.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC P0505 Idle Control System

Conditions for Running the DTC
    • DTCs P0011, P0012, P0031, P0032, P0100, P0101, P0102, P0103, P0115, P0117, P0118, P0120, P0121, P0122, P0123, P0125, P0130, P0133, P0134, P0171, P0172, P0220, P0222, P0223, P0300, P0301-P0304, P0335, P0340, P0341, P0351-P0354, P0385, P0500, P0850, P2102, P2103, P2111, P2112, P2118, P2119, P2120, P2121, P2122, P2123, P2125, P2127, P2128, P2135, P2138 are not set.
    • The battery voltage is more than 11 volts.
    • The engine coolant temperature is at least 75°C (167°F).
    • The engine is running at idle conditions.
    • Vehicle speed has exceeded 10 km/h (6 mph) at least once this drive cycle.
    • DTC P0505 runs continuously once the above conditions have been met.

Conditions for Setting the DTC

The observed engine speed at idle is less than the expected engine speed by 100 RPM or more.

OR

The observed engine speed at idle is more than the expected engine speed by 150 RPM or more.

Either of the above conditions has occurred 5 times or more this drive cycle.

Action Taken When the DTC Sets
    • The PCM illuminates the malfunction indicator lamp (MIL) after 2 consecutive ignition cycles in which the diagnostic runs with the fault active.
    • The PCM stores the conditions which were present when the DTC set as Freeze Frame data.

Conditions for Clearing the MIL/DTC
    • The PCM turns OFF the MIL on the third consecutive trip cycle during which the diagnostic has been run and the fault condition is no longer present.
    • The DTC clears after 40 consecutive warm-up cycles have occurred without a fault.
    • A DTC can be cleared by using the scan tool Clear DTC Information function.

Diagnostic Aids
    • With the engine idling at a normal operating temperature and all accessories OFF, monitor the following parameters on the scan tool:
       - TP sensor--8 to 13 percent
       - Engine speed--650 to 750 RPM
       - Electrical load--NO
       - Commanded A/C--OFF
       - Engine load--11 to 20 percent
       - If any of the above parameters is outside of the typical value as indicated, inspect for the cause and repair as necessary.
    • Inspect for an intermittent condition. Refer to Intermittent Conditions .
    • The information included in the Freeze Frame data can be useful in determining the vehicle operating conditions when the DTC first set.
    • If the DTC P0505 does not reset, but an idle quality symptom still exists, refer to Symptoms - Engine Controls .

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. A Diagnostic System Check - Vehicle prompts the technician to complete some basic checks and store the Freeze Frame data on the scan tool if applicable. This creates an electronic copy of the data taken when the fault occurred. The information is then stored in the scan tool for later reference.

    2.

  2. This step verifies the correct position of the throttle plate. If the TP sensor value at idle is above or below the specified range, DTC P0505 can set.

    3.

  3. This step determines the cause of a too large or too small throttle opening. The fault can be with the throttle body or with the throttle actuator control (TAC) module.

Step

Action

Value(s)

Yes

No

1

Did you perform A Diagnostic System Check - Vehicle?

--

Go to Step 2

Go to Diagnostic System Check - Vehicle

2

Are there any other DTCs set?

--

Go to Diagnostic Trouble Code (DTC) List - Vehicle

Go to Step 3

3
  1. Start the engine.
  2. Run the engine until a normal operating temperature of at least 80°C (174°F) is achieved.
  3. Allow the engine to idle for at least 15 minutes after reaching operating temperatures.
  4. Operate the engine at 2,500 RPM for 90 seconds.
  5. Release the throttle and wait 30 seconds while the engine idle stabilizes.
  6. Observe the Engine Speed and TP Sensor parameters on the scan tool with the transmission in Park or Neutral.

Are the Engine Speed and the throttle position (TP) Sensor within the specified ranges?

650-750 RPM

8-13% TP Sensor

Go to Step 4

Go to Step 5

4

  1. Use the scan tool in order to clear the DTCs.
  2. Turn OFF the ignition for 30 seconds.
  3. Start the engine.
  4. Operate the vehicle within the Conditions for Running the DTC.

Is there a DTC P0505 in Last Test Failed?

--

Go to Step 5

Go to Diagnostic Aids

5

Is the throttle position (TP) sensor value within the specified range?

8-13% TP Sensor

Go to Step 6

Go to Step 10

6

  1. Inspect the positive crankcase ventilation (PCV) system for the following conditions:
    2. • Inspect for the correct operation of the PCV system--Refer to Crankcase Ventilation System Inspection/Diagnosis
    • Inspect for the correct PCV valve--Refer to Positive Crankcase Ventilation Valve Replacement
  2. Repair or replace as necessary.

Did you find and correct the condition?

--

Go to Step 11

Go to Step 7

7
  1. Inspect the intake air system for the following conditions:
    2. • Inspect for any blockage or restrictions
    • Inspect for leaks in the ducts, fittings and gaskets, from the mass air flow (MAF) sensor to the intake manifold.
  2. Repair or replace as necessary.

Did you find and correct the condition?

--

Go to Step 11

Go to Step 8

8
  1. Inspect the throttle body for the following conditions:
    2. • Inspect for any blockage or restrictions in throttle bore
    • Inspect for leaks at the throttle body connections.
    • Inspect for a worn or damaged throttle plate and bore
  2. Repair or replace as necessary. Refer to Throttle Body Assembly Replacement .

Did you find and correct the condition?

--

Go to Step 11

Go to Step 9

9
  1. Inspect the carpet or floor mat for interfering with the free movement of the accelerator pedal.
  2. Inspect for a binding or damaged accelerator pedal assembly.
  3. Repair or replace as necessary. Refer to Accelerator Pedal Position Sensor Replacement .

Did you find and correct the condition?

--

Go to Step 11

Go to Rough, Unstable, or Incorrect Idle and Stalling

10

  1. Inspect the throttle body for the following conditions:
    2. • Inspect for any blockage or restrictions in throttle bore
    • Inspect for excessive carbon deposits on the throttle plate and bore
    • Inspect for a binding or damaged throttle plate and bore
  2. Repair or replace as necessary. Refer to Throttle Body Assembly Replacement .

Did you complete the action?

--

Go to Step 11

--

11
  1. Use the scan tool in order to clear the DTCs.
  2. Turn OFF the ignition for 30 seconds.
  3. Start the engine.
  4. Operate the vehicle within the Conditions for Running the DTC.

Is there a DTC P0505 in Last Test Failed?

--

Go to Step 2

Go to Step 12

12

With a scan tool, observe the stored information, Capture Info.

Does the scan tool display any DTCs that you have not diagnosed?

--

Go to Diagnostic Trouble Code (DTC) List - Vehicle

System OK