For 1990-2009 cars

## DTC P0506 or P0507 w/o TAC

### Diagnostic Instructions

• | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

• | Review Strategy Based Diagnosis for an overview of the diagnostic approach.

• | Diagnostic Procedure Instructions provides an overview of each diagnostic category.

### DTC Descriptors

DTC P0506: Idle Speed Low
DTC P0507: Idle Speed High

### Circuit/System Description

The engine control module (ECM) controls the engine idle speed by adjusting the position of the idle air control (IAC) valve pintle. The IAC valve is a stepper motor driven by two internal coils. The movement of the IAC valve is controlled electrically by four circuits. Drivers within the ECM control the polarity of the two windings inside the IAC valve through these circuits. The ECM, by commanding the correct polarity in sequence, is able to command the motor within the IAC valve to rotate clockwise or counter clockwise in steps. In order for the armature of the stepper motor of the IAC valve to turn one revolution, it needs to move approximately twenty four steps. The IAC valve motor is linked by a gear drive to the IAC valve pintle. The electrical pulses sent to the IAC valve coils, by the ECM, allows the pintle to extend or retract into the passage in the throttle body. By retracting the pintle, air is allowed to bypass the throttle valve, which will increase air flow and raise engine speed. When the pintle is extended, bypass air is decreased which lowers engine speed. IAC valve movement is measured in counts on the scan tool. Each count is equivalent to a step of the IAC valve. When the IAC valve is fully extended, and seated in the throttle body bore, the scan tool displays zero and the engine speed is slow. As the IAC valve pintle retracts the counts will raise along with engine speed.

The IAC valve the following circuits:

• | An IAC Coil A High

• | An IAC Coil A Low

• | An IAC Coil B High

• | An IAC Coil B Low

### IAC Valve Reset

When the ignition switch is turned OFF for more than ten seconds an IAC valve reset occurs. At that time, the ECM commands the IAC valve to extend for a certain period which allows the IAC pintle to seat in the throttle body bore. This position is then sensed as zero count position for the IAC valve by the ECM. It must be observed that the IAC valve position is only sensed by the ECM measuring counts or steps of the driver circuit, there is no direct sensing of its exact position. When this extend time period ends, the ECM then commands the IAC valve to retract a predetermined amount. This will allow for a high engine speed on the next ignition cycle. If for any reason the IAC valve pintle moves after this reset, before the next ignition cycle, the ECM will not be able to detect it and will affect the ability to control engine idle. When the IAC valve is removed for any reason the reset must be performed.

### Conditions for Running the DTC

• | DTCs P0106, P0107, P0108, P0112, P0113, P0117, P0118, P0122, P0123, P0131, P0132, P0133, P0134, P0135, P0171, P0172, P0201, P0202, P0203, P0204, P0300, P0336, P0337, P0341, P0342, P0351, P0352, P0402, P0404, P0405, P0406, P0443, P0502, P1133, P1134, P1166 and P1404 are not set.

• | The engine run time is greater than 60 seconds.

• | The manifold absolute pressure (MAP) is less than 60 kPa.

• | The barometric pressure (BARO) is greater than 72 kPa.

• | The intake air temperature (IAT) is greater than -20°C (-4°F).

• | The engine coolant temperature ( ECT) is greater than 60°C (140°F).

• | The ignition voltage is between 11-16 volts.

• | The DTCs run when the above conditions are met for 5 seconds.

### Conditions for Setting the DTC

#### P0506

The actual engine speed is less than the desired idle speed by at least 100 RPM for 10 seconds.

#### P0507

The actual engine speed is greater than the desired idle speed by at least 200 RPM for 10 seconds.

### Action Taken When the DTC Sets

DTCs P0506, and P0507 are Type B DTCs.

### Conditions for Clearing the DTC

DTCs P0506, and P0507 are Type B DTCs.

### Reference Information

#### Schematic Reference

Engine Controls Schematics

#### Connector End View Reference

Component Connector End Views

#### Electrical Information Reference

• | Circuit Testing

• | Connector Repairs

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

#### DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

#### Scan Tool Reference

Control Module References for scan tool information

#### Special Tools

J 37027-A Idle Air Control Motor Tester

### Circuit/System Verification

Engine running for 1 minute, observe the DTC information with a scan tool. DTCs P0506 or P0507 should not set.

### Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the idle air control (IAC) valve.
2. Connect the J 37027-A to the IAC valve.
3. Engine running, command the IAC valve in until 600 RPM is reached with the J 37027-A , then command the IAC valve out until 1,800 RPM is reached then lower the idle to 800 RPM. The engine speed should steadily increase and decrease as commanded.

⇒ | If the idle does not increase or decrease steadily, verify one of the following conditions is not present:

• | A clogged IAC passage

• | Excessive deposits on the throttle plate or bore

• | Excessive deposits on IAC valve pintle or bore

• | Restricted air intake system

• | The throttle body for damage and/or tampering

• | Vacuum leaks

• | Malfunctioning PCV valve

⇒ | If all conditions test normal, test or replace the IAC valve.

Important: The test lamp is used to load the circuit and may not illuminate.

4. Connect a test lamp between the IAC coil A high control circuit and ground.

• | IAC coil A high control circuit terminal D

• | IAC coil A low control circuit terminal C

• | IAC coil B high control circuit terminal B

• | IAC coil B low control circuit terminal A

Important: This test must be performed on all of the IAC control circuits.

5. Engine running, command the IAC valve out until 1,800 RPM is reached then lower the idle to 800 RPM with the J 37027-A . The test lamp should flash.

⇒ | If the test lamp does not illuminate, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the ECM.

⇒ | If the test lamp does illuminate, but does not flash, test the control circuit for a short to voltage. If the circuit tests normal, replace the ECM.

⇒ | If test lamp illuminates and flashes for all of the control circuits, test the coil control circuits for high resistance. If the circuit tests normal, replace the ECM.

### Component Testing

1. Ignition OFF, disconnect the harness connector at the idle air control (IAC) valve.
2. Test for 40-80 ohms of resistance between the following terminals:

• | A and B

• | C and D

⇒ | If not within the specified range, replace the IAC valve.

3. Test for infinite resistance between the following terminals:

• | A and C

• | B and C

⇒ | If not the specified value, replace the IAC valve.

4. Test for infinite resistance between each terminal and the IAC valve housing.

⇒ | If not the specified value, replace the IAC valve.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Idle Air Control Valve Replacement

• | Control Module References for engine control module replacement, setup, and programming.

## DTC P0506 or P0507 w/TAC

### Diagnostic Instructions

• | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

• | Review Strategy Based Diagnosis for an overview of the diagnostic approach.

• | Diagnostic Procedure Instructions provides an overview of each diagnostic category.

### DTC Descriptors

DTC P0506: Idle Speed Low
DTC P0507: Idle Speed High

### Circuit/System Description

The throttle actuator control (TAC) motor is a DC motor that is part of the throttle body assembly. The TAC motor drives the throttle valve. The engine control module (ECM) controls the TAC motor based on throttle position sensor input. The idle speed is controlled by the ECM based on various inputs. The ECM commands the TAC motor to open or close the throttle valve in order to maintain the desired idle speed.

### Conditions for Running the DTC

#### P0506 or P0507 Euro III Emissions

• | The engine is idling.

• | The engine run time is greater than 2 seconds.

• | The evaporative emission (EVAP) purge flow is less than 100 percent.

• | The barometric pressure (BARO) is greater than 72 kPa.

• | The intake air temperature (IAT) is greater than -20°C (-4°F).

• | The engine coolant temperature (ECT) is greater than -10°C (+14°F).

• | The ignition voltage is between 11-16 volts.

• | The DTCs run when the above conditions are met for 3 seconds.

#### P0506 or P0507 Euro IV Emissions

• | DTCs P0107, P0108, P0112, P0113, P0117, P0118, P0122, P0123, P0131, P0132, P0134, P0135, P0141, P0171, P0172, P0201, P0202, P0203, P0204, P0336, P0337, P0341, P0342, P0351, P0352, P0402, P0404, P0405, P0406, P0443, and P0488 are not set.

• | The engine is idling.

• | The engine run time is greater than 60 seconds.

• | The manifold absolute pressure (MAP) is between 22-60 kPa.

• | The barometric pressure (BARO) is greater than 72 kPa.

• | The intake air temperature (IAT) is greater than -20°C (-4°F).

• | The engine coolant temperature (ECT) is greater than 60°C (140°F).

• | The ignition voltage is between 11-16 volts.

• | The DTCs run when the above conditions are met for 5 seconds.

### Conditions for Setting the DTC

#### P0506

The actual engine speed is less than the desired idle speed by at least 100 RPM for 10 seconds.

#### P0507

The actual engine speed is more than the desired idle speed by at least 200 RPM for 10 seconds.

### Action Taken When the DTC Sets

DTCs P0506, and P0507 are Type B DTCs.

### Conditions for Clearing the DTC

DTCs P0506, and P0507 are Type B DTCs.

### Reference Information

#### Schematic Reference

Engine Controls Schematics

#### Connector End View Reference

Component Connector End Views

#### Electrical Information Reference

• | Circuit Testing

• | Connector Repairs

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

#### DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

#### Scan Tool Reference

Control Module References for scan tool information

### Circuit/System Verification

1. Engine idling within the conditions for running the DTCs for 1 minute. DTCs P0506 or P0507 should not set.
2. Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.

### Circuit/System Testing

#### P0506

• | Inspect the engine for vacuum leaks.

• | Inspect the throttle valve for the correct operation--A throttle valve that does not close correctly sets this DTC.

• | Verify the correct operation of the crankcase ventilation system--Inspect for the following conditions:

- | The routing of the PCV system

- | Vacuum leaks in the PCV system

#### P0507

• | Inspect for excess deposits in the throttle body.

• | Inspect for a parasitic load on the engine--For example, a transmission condition, a belt driven accessory condition.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Throttle Body Assembly Replacement

• | Control Module References for engine control module replacement, setup, and programming