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 greater than 4 volts at wide open throttle (WOT).

If a shared 5-volt reference circuit is shorted to ground or shorted to a voltage, other 5-volt reference circuits may be affected.

Schematic Reference

Engine Controls Schematics

Connector End View Reference

Engine Control Module Connector End Views

Electrical Information Reference

Scan Tool Reference

Engine Control Module Scan Tool Information

1. Ignition ON, observe the DTC information with a scan tool. Verify DTC 81-5 Volt Reference Circuit out of Range is not set.

⇒	If DTC 81-5 Volt Reference Circuit out of Range is set, refer to DTC 81 for further diagnosis.

2. Ignition ON, slowly depress the accelerator pedal from the rest position to wide open throttle and observe the scan tool TP Sensor voltage parameter. The voltage should change.
3. Engine idling, observe the DTC information with a scan tool. DTC 21 or 22 should not set.

1. Ignition OFF, disconnect the harness connector at the throttle body assembly.
2. Test for less than 5 ohms between the low reference circuit terminal B and ground.

⇒	If greater than the specified range, test the low reference circuit for a short to voltage, or an open/high resistance. If the circuit tests normal, replace the ECM.

3. Ignition ON, test for 4.8-5.2 volts between the 5-volt reference circuit terminal A and ground.

⇒	If less than the specified range, test the 5-volt reference circuit for a short to ground or open/high resistance. If the circuit tests normal, replace the ECM.

⇒	If greater than the specified range, test the 5-volt reference circuit for a short to voltage. If the circuit tests normal, replace the ECM.

4. Test for 4.8-5.2 volts between the signal circuit terminal A and ground.

⇒	If less than the specified range, test the signal circuit for an open or a short to ground. If the circuit tests normal, replace the ECM.

⇒	If greater than the specified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the ECM.

5. If all circuits test normal, replace the throttle position sensor.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.