P0123

DTC P0123: Throttle Position (TP) Sensor 1 Circuit High Voltage





Circuit Description
The throttle body assembly contains 2 Throttle Position (TP) sensors. The TP sensors are mounted to the throttle body assembly and are not serviceable. The TP sensors provide a signal voltage that changes relative to throttle plate angle. The Engine Control Module (ECM) supplies the TP sensors with a common 5 volt reference circuit, a common low reference circuit, and 2 independent signal circuits.
The TP sensors have opposite functionality. TP sensor 1 signal voltage increases from below 1 V at idle to above 4 V at Wide Open Throttle (WOT). TP sensor 2 signal voltage decreases from above 4 V at idle to below 1 V at WOT.

Conditions for Setting the DTC
- Ignition ON.
- No TP sensor fault exists.
- TPS voltage is greater than 4.75 V.

Action Taken When the DTC Sets
- The Malfunction Indicator Lamp (MIL) will illuminate.
- The ECM will record operating conditions at the time the diagnostic fails. This information will be stored in the Freeze Frame and Failure Records buffers.
- A history DTC is stored.

Conditions for Clearing the MIL/DTC
- The MIL will turn OFF after four consecutive validation cycles in which the diagnostic runs without a fault.
- A history DTC will clear after 40 consecutive warm up cycles without a fault.
- The DTC(s) can be cleared by using the scan tool.

Diagnostic Aids
If the DTC P0123 cannot be duplicated, the information included in the Freeze Frame data can be useful. Use the scan tool DTC information data to determine the status of the DTC. If the DTC occurs intermittently, using the DTC P0121 diagnostic table may help isolate the problem.

Test Description
Number(s) below refer to the step number(s) on the Diagnostic Table.
1. This step verifies that a condition exists.
2. This step tests the signal circuit for a short to voltage. If the scan tool displays a voltage after the TP sensor is disconnected, the circuit is shorted to a voltage.
3. This step tests for high resistance in the low reference circuit of the TP sensor. The ECM must be completely powered down to obtain an accurate resistance reading. It may take up to 30 minutes for the ECM to power down after the ignition key is removed. Removal of the ECM/TCM fuse allows the ECM to power down completely.
4. This step tests the low reference circuit for a short to voltage.

Step 1-10:

Step 11-18:

Troubleshooting