For 1990-2009 cars

### 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 provide 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 controlled by the engine control module (ECM). The DC motor located in the throttle body drives the throttle blade. In order to decrease idle speed, along with spark and fuel delivery changes the ECM commands the throttle closed reducing air flow into the engine and the idle speed decreases. In order to increase idle speed, the ECM commands the throttle plate open allowing more air to pass the throttle plate.

### Conditions for Running the DTC

• | DTCs P0068, P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0117, P0118, P0120, P0122, P0123, P0171, P0172, P0201, P0202, P0203, P0204, P0205, P0206, P0207, P0208, P0220, P0221, P0222, P0223, P0230, P0300, P0336, P0442, P0446, P0449, P0452, P0453, P0455, P0462, P0463, P0496, P1516, P2101, P2135, P2176 are not set.

• | The engine is operating for at least 60 seconds.

• | The engine is idling for greater than 10 seconds.

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

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

• | The barometric pressure (BARO) is more than 70 kPa.

• | The system voltage is between 9-18 volts.

• | The vehicle speed is less than 1.6 km/h (1 mph).

• | DTC P0506 and P0507 run continuously when the above conditions are met.

### Conditions for Setting the DTC

#### P0506

The actual idle speed is approximately 100 RPM lower than the desired idle speed.

#### P0507

The actual idle speed is approximately 200 RPM greater than the desired idle speed.

### Action Taken When the DTC Sets

DTCs P0506 and P0507 are Type B DTCs.

### Conditions for Clearing the MIL/DTC

DTCs P0506 and P0507 are Type B DTCs.

### Diagnostic Aids

• | A stalling condition can cause DTC P0506 to set.

• | An intermittent vehicle speed sensor (VSS) signal can cause DTC P0507 to set.

• | An intermittent clutch pedal position sensor signal, if equipped, can cause DTC P0506 to set.

### 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

Important: The engine must first be running for greater than 60 seconds, then idle at a steady state for an additional 10 seconds before comparing the actual and desired engine idle speed parameters.

1. Use a scan tool to compare the desired engine idle speed to the actual engine idle speed.

⇒ | Actual engine idle speed should be no greater than 100 RPM below desired.

⇒ | Actual engine idle speed should be no greater than 200 RPM above desired.

2. If any other DTCs are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle.
3. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.

### Circuit/System Testing

1. Inspect for any condition that can reduce idle speed by increasing engine load.

• | Incorrect torque converter clutch (TCC) operation

• | Accessories that require additional torque to operate

• | Excessive deposits in the throttle body

• | Restricted exhaust

• | Mechanical conditions that limit engine speed

• | Repair any conditions, if necessary.

2. Inspect for the following conditions:

• | Vacuum leaks

• | A faulty positive crankcase ventilation (PCV) valve

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.