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 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 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, P0107, P0108, P0112, P0113, P0117, P0118, P0120, P0122, P0123, P0125, P0171, P0172, P0201, P0202, P0203, P0204, P0220, P0300, P0336, P0442, P0446, P0452, P0453, P0641, P0651, P1516, P2101, P2135, P2176 are not set.

• | The engine is operating for at least 2 seconds.

• | The engine coolant temperature (ECT) is more than -40°C (-40°F).

• | The intake air temperature (IAT) is more than -40°C (-40°F).

• | The barometric pressure (BARO) is more than 65 kPa.

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

• | The vehicle speed is less than 4.8 km/h (3 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 120 RPM lower than the desired idle speed.

• | The above condition is present for 15 seconds.

#### P0507

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

• | The above condition is present for 15 seconds.

### Action Taken When the DTC Sets

DTC P0506 and P0507 are Type B DTCs.

### Conditions for Clearing the MIL/DTC

DTC P0506 and P0507 are Type B DTCs.

### Reference Information

#### Schematic Reference

Engine Controls Schematics

#### Connector End View Reference

Component Connector End Views

#### Description and Operation

Throttle Actuator Control (TAC) System Description

#### 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. If there are any other DTCs set, refer to Diagnostic Trouble Code (DTC) List - Vehicle for further diagnosis.
2. Compare the desired engine idle speed to the actual engine idle speed with a scan tool. Actual engine idle speed should be no greater than or less than 100 RPM of desired RPM.
3. Command the engine speed up and down with a scan tool. Increase the engine speed in 25 RPM increments while comparing the desired engine speed to the actual engine speed. The actual engine speed should stay within 25 RPM of the desired engine speed.
4. 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--Refer to Throttle Body Cleaning .

• | Restricted exhaust--Refer to Restricted Exhaust .

• | Mechanical conditions that limit engine speed

5. Inspect for any condition that can increase idle speed.

• | Vacuum leaks

• | Unmetered air entering the engine after the mass air flow

• | A faulty positive crankcase ventilation (PCV) valve