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:

Idle Switch Open

Idle Switch Closed

The ECM detects an open or a short to ground on the idle position signal circuit of the ISC motor.

DTC P0510 is a Type B DTC.

DTC P0510 is a Type B DTC.

Schematic Reference

Engine Controls Schematics

Description and Operation

Idle Speed Control System Description

Electrical Information Reference

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

1. Ignition ON, engine OFF observe the scan tool idle switch parameter 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.

1. Ignition OFF, disconnect the harness connector at the ISC motor.
2. Ignition OFF, test for less than 5 ohms of resistance 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 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 signal circuit terminal 4 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 short to voltage on the signal circuit.

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

1. Ignition OFF, disconnect the harness connector at the ISC motor.
2. Test the resistance between the idle switch position terminal 4 and low reference circuit terminal 8.

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

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.