GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Pontiac 🢒 2004 🢒 GTO 🢒 Engine 🢒 Engine Controls - 5.7L 🢒 DTC P0506 or P0507

Circuit Description

The DTC P0506 Idle Speed Low diagnostic monitors the engine speed. The powertrain control module (PCM) controls the idle air control (IAC) valve in order to regulate the air flow through the idle air bypass passage. The amount of air flowing through the idle air bypass passage determines the idle speed. The PCM directs the IAC valve according to changes in the engine load. A stalling or poor idle concern may be caused by the IAC valve not operating properly.

DTC Descriptors

This diagnostic procedure supports the following DTC.

DTC P0506 Idle Speed Low

Conditions for Running the DTC
    • DTCs P0101, P0102, P0103, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0121, P0122, P0123, P0125, P0128, P0131, P0132, P0133, P0134, P0135, P0137, P0140, P0141, P0151, P0152, P0153, P0154, P0155, P0157, P0158, P0160, P0171, P0172, P0174, P0175, P0452, P0453, P0502, P0503, P0641, P0651, P1111, P1112, P1114, P1115, P1121, P1122, P1133, P1134, P1153, and P1154 are not set.
    • The system voltage is between 9-18 volts.
    • The startup ECT is more than 60°C (39-86°F).
    • The startup IAT is between 4-30°C (39-86°F).
    • The start up ECT and IAT are within 8°C (14°F) of each other.
    • The fuel tank level is between 15-85 percent.
    • The startup barometric pressure (BARO) is more than 65 kPa.
    • The vehicle speed sensor (VSS) is less than 90 km/h (75 mph).
    • DTC P0507 runs once per ignition cycle when the above conditions are met.

Conditions for Setting the DTC
    • The actual engine speed is 100 RPM less than the desired engine speed value with the IAC Motor Command near 0 percent.
    • The above condition exists for more than 5 seconds.

Action Taken When the DTC Sets
    • The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
    • The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

Conditions for Clearing the MIL/DTC
    • The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
    • A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
    • A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
    • Clear the MIL and the DTC with a scan tool.

Diagnostic Aids

Inspect for the following conditions:

    • High resistance in an IAC circuit
    •  Restricted air intake system
    • Proper operation and installation of all air intake components
    • Collapsed, clogged, or loose air intake ducts
    • A clogged air filter
    • Proper operation of the mass air flow sensor, if equipped
    • A tampered with or damaged throttle stop screw
    • A tampered with or damaged throttle plate, throttle shaft, or throttle linkage
    • Objects blocking the IAC passage or throttle bore
    • Excessive deposits in the IAC passage or on the IAC pintle
    • Excessive deposits in the throttle bore or on the throttle plate
    • Vacuum leaks
    • A low or unstable idle condition could be caused by a non-IAC system problem that can not be overcome by the IAC valve--Refer to Symptoms - Engine Controls

If the problem is determined to be intermittent, refer to Intermittent Conditions .

Test Description

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

  1. This test will determine the ability of the engine controller and the IAC valve circuits to control the IAC valve.

    2.

  2. This test will determine the ability of the PCM to provide the IAC circuits with a ground. On a normally-operating system, the test lamp should not flash while the IAC counts are incrementing.

Step

Action

Yes

No

Schematic Reference: Engine Controls Schematics

1

Did you perform the Diagnostic System Check-Engine Controls?

Go to Step 2

Go to Diagnostic System Check - Engine Controls

2

Important:  Ensure engine speed stabilizes with each commanded RPM change to determine if engine speed stays within 100 RPM of the commanded RPM.

  1. Set the parking brake and block the drive wheels.
  2. Install a scan tool.
  3. Start the engine.
  4. Turn OFF all of the accessories.
  5. With the scan tool RPM control function slowly increment engine speed to 1,700 RPM, then to 600 RPM, then to 1,700 RPM.
  6. Exit the RPM control function.

Does the engine speed stabilize within 100 RPM of the commanded RPM during the above test?

Go to Step 3

Go to Step 4

3
  1. Observe the Freeze Frame/Failure Records for this DTC.
  2. Turn OFF the ignition for 30 seconds.
  3. Start the engine.
  4. Operate the vehicle within the Conditions for Running the DTC, and within the parameters observed in the Freeze Frame/Failure Records.

Does the DTC fail this ignition?

Go to Step 4

Go to Diagnostic Aids

4
  1. Turn OFF the ignition.
  2. Disconnect the IAC valve.
  3. Connect an J 37027-1A IAC Motor Driver to the IAC valve.
  4. Start the engine.
  5. With the J 37027-1A , command the IAC valve in until near 600 RPM is reached.
  6. With the J 37027-1A , command the IAC valve out until near 1,700 RPM is reached.
  7. Return engine speed to desired idle as indicated on the scan tool data list.

Did the engine speed steadily decrease to near 600 RPM and steadily increase to near 1,700 RPM when the IAC valve was commanded in and out?

Go to Step 5

Go to Step 11

5

  1. With a test lamp connected to ground, probe one of the IAC valve circuits at the IAC valve harness connector using the J 35616 Connector Test Adapter Kit .
  2. Start the engine.
  3. With the J 37027-1A , command low RPM while observing a scan tool until the IAC counts start to increment.
  4. With the J 37027-1A , command high RPM while observing a scan tool until the IAC counts start to increment.
  5. While the IAC counts are incrementing observe the test lamp.
  6. Return engine idle speed to desired idle as indicated on the scan tool data list.
  7. Repeat the above procedure for the other three IAC valve circuits.

Did the test lamp remain ON, never flashing, while the IAC counts where incrementing at any of the IAC valve circuits during the above test?

Go to Step 10

Go to Step 6

6

Did the test lamp remain OFF, never flashing, while the IAC counts where incrementing at any of the IAC valve circuits during the above test?

Go to Step 9

Go to Step 7

7

  1. Connect a test lamp between the IAC coil A low circuit and the IAC coil A high circuit at the IAC valve harness connector using the J 35616 .
  2. With the J 37027-1A , command low RPM while observing a scan tool until the IAC counts start to increment.
  3. With the J 37027-1A , command high RPM while observing a scan tool until the IAC counts start to increment.
  4. While the IAC counts are incrementing, observe the test lamp.
  5. Return engine idle speed to desired idle as indicated on the scan tool data list.
  6. Repeat the above procedure with the test lamp connected between the IAC coil B low circuit and the IAC coil B high circuit at the IAC valve harness connector.
  7. Return engine speed to the desired idle as indicated on the scan tool data list.

Did the test lamp stay illuminated and never flashing while the IAC counts where incrementing during the above test?

Go to Step 8

Go to Step 16

8

Inspect for a poor connection at the IAC valve harness connector. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 17

Go to Step 12

9
  1. Turn OFF the ignition.
  2. Disconnect the PCM harness connectors.
  3. With a DMM, test the circuit where the test lamp remained OFF for the following conditions:
    4. • An open circuit
    • A short to ground
    • A short to another IAC valve circuit
  4. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 17

Go to Step 12

10
  1. Turn ON the ignition.
  2. With a DMM, test the circuit where the test lamp remained ON for the following conditions:
    3. • A short to voltage
    • A short to another IAC valve circuit
  3. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 17

Go to Step 12

11
  1. Visually/Physically inspect for the following:
    2. • Throttle body damage and tampering
    • Throttle lever screw tampering, if equipped
    • Restricted air intake system--Inspect for a possible collapsed/clogged air intake duct, before and after the air filter element, restricted air filter element, restriction at the throttle body intake screen, if equipped.
  2. Remove the IAC valve. Refer to Idle Air Control Valve Replacement .
  3. Inspect for the following conditions:
    4. • A clogged IAC passage
    • Excessive deposits on the throttle plate
    • Excessive deposits in the throttle bore
    • Excessive deposits on IAC valve pintle
  4. Repair any of the above conditions as necessary. Refer to the appropriate repair procedure.

Did you find and correct the condition?

Go to Step 17

Go to Step 14

12

Inspect for a poor connection at the PCM harness connectors. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 17

Go to Step 13

13
  1. Disconnect the PCM harness connectors.
  2. With a DMM, test all IAC valve circuits for high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 17

Go to Step 16

14

Inspect for a poor connection at the IAC valve harness connector. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 17

Go to Step 15

15

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

Did you complete the replacement?

Go to Step 17

--

16

Replace the PCM. Refer to Powertrain Control Module Replacement .

Did you complete the replacement?

Go to Step 17

--

17
  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 as specified in the supporting text.

Does the DTC run and pass?

Go to Step 18

Go to Step 2

18

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

System OK