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
DTC P050A: Cold Start Idle Air Control (IAC) System Performance

### 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

#### P0506 and P0507

• | DTC P0111, P0112, P0113, P0116, P0117, P0118, P0119, P0121, P0122, P0123, P0221, P0222, P0223, P0442, P0443, P0446, P0455, P0458, P0459, P0496, P0497, or P0700 is not set.

• | The intake air temperature (IAT) is greater than -11°C (+13°F).

• | The engine coolant temperature (ECT) is greater than -11°C (+13°F).

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

• | The engine is idling.

• | The engine is operating for greater than 4 seconds.

• | The evaporative emission (EVAP) system intrusive test is not active.

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

• | The DTCs run continuously once the above conditions are met for greater than 10 seconds.

#### P050A

• | DTC P0111, P0112, P0113, P0116, P0117, P0118, P0119, P0121, P0122, P0123, P0221, P0222, P0223, P0442, P0443, P0446, P0455, P0458, P0459, or P0700 is not set.

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

• | The engine is idling.

• | The ECT is less than 65°C (149°F) at cold start.

• | The cold start idle speed control is enabled.

• | The ECT is less than 60°C (140°F) for the duration of the test.

• | DTC P050A runs once an ignition cycle when the conditions above have been met for 7 seconds.

### Conditions for Setting the DTC

#### P0506

The actual engine speed is less than the desired idle speed by at least 100 RPM for greater than 4 seconds or for a cumulative of 30 seconds.

#### P0507

The actual engine speed is greater than the desired idle speed by at least 200 RPM for greater than 4 seconds or for a cumulative of 30 seconds.

#### P050A

• | The actual engine speed is less than the desired idle speed by at least 100 RPM for greater than 4 seconds or a cumulative of 30 seconds, during a cold start.

| OR

• | The actual engine speed is less than the desired idle speed by at least 200 RPM for greater than 4 seconds or a cumulative of 30 seconds, during a cold start.

### Action Taken When the DTC Sets

DTCs P0506, P0507, and P050A are Type B DTCs.

### Conditions for Clearing the DTC

DTCs P0506, P0507, and P050A 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

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. Observe the DTC information with a scan tool.

⇒ | If there are any throttle actuator control (TAC), throttle position (TP) sensor, accelerator pedal position (APP) sensor, or fuel rail pressure (FRP) regulator 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, P0507, or P050A should not set.
3. 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

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 system

• | 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.