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 Descriptor

DTC P0510: Idle Position Switch Circuit

### Circuit Description

The throttle body assembly contains an idle speed control (ISC) motor that is used to control the engine speed at idle. The engine control module (ECM) commands the ISC motor to adjust the throttle angle for idle speed control. An idle switch is also integrated into the throttle body assembly. The idle switch position is dependant upon the position of the throttle. The ECM receives an ON signal from the idle switch when the throttle is at idle and receives an OFF signal from the switch when the throttle is open.

The following table illustrates the correlation between the idle switch and the throttle position:

Throttle Position | Idle Switch | Idle Switch Parameter
--- | --- | ---
Closed | Open | ON
Open | Closed | OFF

### Conditions for Running the DTC

#### Idle Switch Open

• | DTCs P0122, P0123, P0222, P0223, P2101, P2118, and P2119 are not set.

• | Ignition is ON.

• | The throttle position is closed.

• | DTC P0510 runs continuously once the above condition is met.

#### Idle Switch Closed

• | DTCs P0122, P0123, P0222, and P0223 are not set.

• | The engine is operating.

• | The throttle position is greater than 35 degrees.

• | DTC P0510 runs continuously once the above condition is met.

### Conditions for Setting the DTC

• | The ECM detects that the idle switch signal is OFF when the throttle is less than 10 degrees for more than 2 seconds.

| Or

• | The ECM detects that the idle switch signal is ON when the throttle is more than 35 degrees for more than 0.2 second.

### Action Taken When the DTC Sets

DTC P0510 is a Type A DTC.

### Conditions for Clearing the MIL/DTC

DTC P0510 is a Type A DTC.

### 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. Ignition ON, engine OFF. Observe the idle switch parameter with a scan tool while slowly depressing the accelerator pedal to wide open throttle. The idle switch parameter should change from ON, to OFF when the accelerator pedal is depressed.
2. 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

1. Ignition OFF, disconnect the harness connector at the idle speed control (ISC) motor.
2. Ignition OFF, test for less than 5 ohms between the low reference circuit terminal 8 and ground.

⇒ | If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the ECM.

3. Ignition ON, verify the scan tool Idle Switch parameter displays OFF.

⇒ | If the parameter displays ON, test the signal circuit for a short to ground. If the circuit tests normal, replace the ECM.

4. Install a 3A fused jumper wire between the idle switch circuit terminal 6 and ground. Verify the scan tool Idle Switch parameter displays ON.

⇒ | If the parameter displays OFF, test the signal circuit for an open. If the circuit tests normal, replace the ECM.

⇒ | If the fuse in the jumper wire opens, repair the signal circuit for a short to voltage.

5. If all circuits test normal, test or replace the throttle body.

### Component Testing

1. Ignition OFF, disconnect the harness connector at the ISC motor.
2. Test the resistance between the idle switch position terminal 6 and low reference terminal 8.

⇒ | If the resistance does not change as the throttle is opened and closed, replace the throttle body.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Throttle Body Assembly Replacement

• | Control Module References for engine control module replacement, setup, and programming