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 plate. To decrease the engine 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 P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0116, P0117, P01118, P0120, P0122, P0123, P0128, P0171, P0172, P0174, P0175, P0201, P0208, P0220, P0222, P0223, P0300, P0301, P0308, P0336, P0440, P0442, P0443, P0446, P0452, P0453, P0496, P0502, P0503, P0641, P0651, P1516, P2101, P2135, P2176 are not set.

• | VSS DTCs are not set.

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

• | The Engine Coolant Temperature (ECT) is greater than 60°C (140°F).

• | The Intake Air Temperature (IAT) is more than -10°C (14°F).

• | The Barometric Pressure (BARO) is more than 65 kPa.

• | The system voltage is between 10.5-18 volts.

• | The engine running time at a stable idle lasts more than 2 seconds.

• | After switching range is more than 3 seconds.

• | After switching the torque converter clutch pattern is more than 3 seconds.

• | The engine is in idle speed status.

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

### Conditions for Setting the DTC

#### P0506

• | The actual engine idle speed is less than the desired.

• | The above condition is present for 12 seconds.

#### P0507

• | The actual engine idle speed is greater than the desired.

• | The above condition is present for 12 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

• | Engine Controls Connector End Views

• | Engine Control Module 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

Diagnostic Trouble Code (DTC) Type Definitions

#### Scan Tool Reference

• | Scan Tool Data List

• | Scan Tool Data Definitions

• | Engine Control Module Scan Tool Information

### Circuit/System Verification

1. If any other DTCs are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle .
2. Compare the desired engine idle speed with the actual engine idle speed with a scan tool. Actual engine idle speed is no greater than or less than 100 RPM of desired.
3. Command the engine speed increase or decrease with a scan tool. Increase the engine speed in 25 RPM increments while comparing the desired engine speed with 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.

• | Torque Converter Clutch (TCC) is improper operation

• | Accessories that require additional torque to operate

• | Excessive deposits in the throttle body--Refer to Throttle Body Inspection and Cleaning .

• | Restricted exhaust system--Refer to Restricted Exhaust .

• | Mechanical conditions that limit engine speed

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

• | Vacuum leak

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

• | A faulty positive crankcase ventilation (PCV) valve

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.