P0123

P0123 Throttle Position Sensor High Voltage




Circuit Description
The powertrain control module (PCM)/engine control module (ECM) supplies a 5 volt reference signal and a ground to the Throttle Position (TP) sensor. The TP sensor sends a voltage signal back to the PCM/ECM relative to the throttle plate opening. The voltage signal will vary from approximately 0.45 volts at closed throttle, to over 4.5 volts at Wide Open Throttle (WOT).

Conditions for Setting the DTC
- TP sensor voltage is greater than 4.9 volts.

Action Taken When the DTC Sets
- The Malfunction Indicator Lamp (MIL) will illuminate.
- The PCM/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 Diagnostic Trouble Code (DTC) is stored.
- The TP angle will default to 0% when the vehicle speed is less than 2 mph (3 kph) and 10% when the vehicle speed is greater than 2 mph (3 kph). (The scan tool will display the defaulted value.)

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

Diagnostic Aids
If a 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.

With the ignition ON and the throttle at closed position, the voltage should read between 0.20 volts and 0.90 volts and increase steadily to over 4.5 volts at WOT.

DTCs P0123 and P0113 stored at the same time could be the result of an open sensor ground circuit.

Step 1 - 11:

Step 12 - 13:

Test Description
Number(s) below refer to the step number(s) on the Diagnostic Table.
1. The On-Board Diagnostic (OBD II) System Check prompts the technician to complete some basic checks and store the freeze frame and failure records data on the scan tool if applicable. This creates an electronic copy of the data taken when the malfunction occurred. The information is then stored on the scan tool for later reference.
2. With the throttle closed, the TP sensor voltage should read less than 0.90 volts. If the TP sensor voltage does not read less than 0.90 volts check for a binding or sticking throttle cable.
4. With the TP sensor disconnected, the TP sensor voltage should be less than 0.2 volts if the PCM/ECM and wiring are OK.
5. Probing the ground circuit with a test light checks the circuit for high resistance which will cause a DTC P0123 to set.
7. A shorted 5 volt reference circuit will also set additional DTCs.
11. The replacement PCM/ECM must be reprogrammed. Refer to the latest Techline procedure for PCM/ECM reprogramming.