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 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. If the ECM detects the actual idle speed and the desired idle speed are not within a predetermined amount, this DTC sets.

### Conditions for Running the DTC

• | DTCs P0111, P0112, P0113, P0116, P0117, P0118, P0119, P0121, P0122, P0123, P0221, P0222, P0223, P0443, P0458, and P0459 are not set.

• | The volumetric efficiency is less than 35 percent, DTC P0506 only.

• | The vehicle speed is 0 km/h (0 mph).

• | The evaporative emission (EVAP) canister purge valve is OFF.

• | The intake air temperature (IAT) is more than -10.5°C (+13°F).

• | The engine coolant temperature (ECT) is greater than -10.5°C (+13°F).

• | A vehicle speed was detected prior to the diagnostic running.

• | DTC P0506 and P0507 run continuously once the above conditions are met for more than 10 seconds.

### Conditions for Setting the DTC

#### P0506

The actual engine speed is less than the desired idle speed by at least 100 RPM for5 seconds.

#### P0507

• | The actual engine speed is more than the desired idle speed by at least 200 RPM for 5 seconds.

| OR

• | The ECM detects 3 fuel cut-offs due to an engine over speed condition while the engine is idling.

### 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.

### Diagnostic Aids

Inspect for a condition in which the throttle valve may have been held open. For example, ice may have formed in the throttle bore.

### Reference Information

#### Schematic Reference

Engine Controls Schematics

#### Connector End View Reference

• | Engine Control Module Connector End Views

• | Engine Controls 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

• | Scan Tool Data List

• | Scan Tool Data Definitions

• | Scan Tool Output Controls

### Circuit/System Verification

1. Observe the DTC information with a scan tool.

⇒ | If there are any throttle actuator control (TAC), throttle position (TP) sensor, or accelerator pedal position (APP) sensor DTCs set, refer to Diagnostic Trouble Code (DTC) List - Vehicle .

2. Operate the engine within the conditions for running the DTCs for 1 minute. DTC P0506 or P0507 should not set.
3. If the vehicle passes the Circuit/System Verification test, you may also operate the vehicle within the conditions that are captured in the Freeze Frame/Failure Records List.

### Circuit/System Testing

Engine operating, command the engine speed up to 1,400 RPM, down to 600 RPM, up to 1,400 RPM, and then exit using the scan tool. The engine speed should steadily increase and decrease as commanded.

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

• | Vacuum leaks

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

• | Restricted air intake system

• | The throttle body for damage and/or tampering

• | Incorrect or malfunctioning PCV valve

• | Excess deposits in the throttle body

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

⇒ | Repair the condition as necessary.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.