Diagnostic Instructions

DTC Descriptors

DTC P0122: Throttle Position (TP) Sensor Circuit Low Voltage

DTC P0123: Throttle Position (TP) Sensor Circuit High Voltage

Diagnostic Fault Information

Circuit	Short to Ground	Open/High Resistance	Short to Voltage	Signal Performance
5-Volt Reference	P0122	P0122	P0123	--
TP Sensor Signal	P0122	P0122	P0123	--
Low Reference	--	P0123	--	--

Circuit/System Description

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).

Conditions for Running the DTC

Conditions for Setting the DTC

DTC P0122: The ECM detects that the TP sensor voltage is less than 0.1 volt.

DTC P0123: The ECM detects that the TP sensor voltage is more than 4.8 volts.

Action Taken When the DTC Sets

DTC P0122 and P0123 are Type A DTCs.

Conditions for Clearing the DTC

DTC P0122 and P0123 are Type A DTCs.

Reference Information

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

Circuit/System Verification

1. 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.
2. If the vehicle passes the Circuit/System Verification test, then operate the vehicle within the conditions for running the DTC. You may also operate the vehicle within the conditions that are captured in the Freeze Frame/Failure Records Data List.

Circuit/System Testing

1. Ignition OFF, disconnect the harness connector of the TP sensor.
2. Ignition ON, verify the scan tool TP Sensor voltage parameter is less than 0.3 volt.

⇒	If greater than 0.3 volt, test the signal circuit of the TP sensor for a short to voltage. If the circuit/connections test normal, replace the 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 ground.
4. Test for 4.8-5.2 volts between the 5-volt reference circuit of the TP sensor and 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 volt between the low reference circuit of the TP sensor and ground.

⇒	If greater than 0.2 volt, 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 for 30 seconds, test for less than 5 ohms of resistance between the low reference circuit of the TP sensor and 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 ECM.

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

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

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