The throttle body assembly contains a throttle position (TP) sensor. The TP sensor is mounted externally on the throttle body assembly. The TP sensor is a potentiometer which provides a signal voltage that changes relative to the throttle blade angle. The engine control module (ECM) supplies the TP sensor with a 5-volt reference circuit, a low reference circuit, and a signal circuit. The TP sensor signal voltage decreases from less than 1 volt at idle to more than 4 volts at wide open throttle (WOT).

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Schematic Reference

Engine Controls Schematics

Connector End View Reference

Electrical Information Reference

Scan Tool Reference

Start the engine, observe the TP Sensor voltage parameter with a scan tool. The parameters should be between 0.4-4.5 volts.

1. Ignition OFF, disconnect the harness connector of the TP sensor.
2. Ignition ON, verify that the TP sensor voltage parameter is less than 0.3 volts.

⇒	If greater than 0.3 volts, test the signal circuit of the TP sensor for a short to voltage. If the circuit/connections test normal, replace the engine control module (ECM).

Important: The test lamp is used to load the circuit and may not illuminate.

3. Ignition ON, connect a test lamp between the 5-volt reference circuit of the TP sensor and a good ground.

Important: The 5-volt reference circuits are internally and externally connected at the ECM. Other component DTCs may be set. If other DTCs are set, review the electrical schematic and diagnose the applicable circuits and components.

4. Test for 4.8-5.2 volts between the 5-volt reference circuit of the TP sensor and a good ground.

⇒	If less than 4.8 volts, test the 5-volt reference circuit of the TP sensor for a short to ground or open/high resistance. If the circuit/connections test normal, replace the ECM.

⇒	If greater than 5.2 volts, test the 5-volt reference circuit of the TP sensor for a short to voltage. If the circuit/connections test normal, replace the ECM.

5. Ignition ON, test for less than 0.2 volts between the low reference circuit of the TP sensor and a good ground.

⇒	If greater than 0.2 volts, test the low reference circuit of the TP sensor for a short to voltage. If the circuit/connections test normal, replace the ECM.

6. Ignition OFF, test for less than 5 ohms of resistance between the low reference circuit of the TP sensor and a good ground.

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

7. Ignition ON, install a 3-amp fused jumper wire between the signal circuit and the 5-volt reference circuit of the TP sensor to verify that the TP sensor voltage parameter is greater than 4.8 volts.

⇒	If less than 4.8 volts, test the appropriate signal circuit of the TP sensor for a short to ground or an open/high resistance. If the circuit/connections test normal, replace the engine control module (ECM).

8. If all circuits/connections test normal, test or replace the TP sensor.

1. Turn OFF the ignition.
2. Measure for 5150-5350 ohms between the 5-volt reference and the low reference terminals of the TP sensor .

⇒	If the resistance is not within the specified range, replace the TP sensor.

3. Measure the resistance between the signal terminal and the low reference terminal of the TP sensor. Slowly sweep the TP sensor through the entire range several times. The resistance should vary between 2500 and 6800 ohms without any spikes or dropouts.

⇒	If the resistance is not within the specified range or is erratic, replace the TP sensor.

4. Apply 5-volts and ground to the applicable terminals of the TP sensor, and measure the voltage between the signal and the low reference terminals. Slowly sweep the TP sensor through the entire range several times. The voltage should vary between 0.6V and 4.7 volts without any spikes or dropouts.

⇒	If the voltage is not within the specified range or is erratic, replace the TP sensor.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.