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

Connector End View Reference

Electrical Information Reference

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

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.

1. Ignition OFF, disconnect the harness connector of the ISC motor.
2. Ignition ON, verify the Idle Switch parameter displays OFF.

⇒	If the Idle Switch parameter displays ON, test the idle switch signal circuit for a short to ground. If the circuit/connections test normal, replace the ECM.

3. Install a 3-amp fused jumper wire between the idle switch signal circuit and battery ground. Verify the Idle Switch parameter displays ON.

⇒	If the Idle Switch parameter displays OFF, test the idle switch signal circuit for an open. If the circuit/connections test normal, replace the ECM.

⇒	If the fuse in the jumper wire opens, repair the short to voltage on the idle switch signal circuit.

4. Ignition OFF, test for less than 5 ohms of resistance between the low reference circuit of the ISC motor and ground.

⇒	If greater than 5 ohms, test the low reference circuit of the ISC motor for an open/high resistance. If the circuit/connections test normal, replace the ECM.

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

1. Ignition OFF, disconnect the harness connector of the ISC motor.
2. Measure the resistance between the idle switch position terminal and low reference circuit terminal of the ISC motor.

⇒	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.