P0123
DTC P0123 Throttle Position (TP) Sensor Circuit High Input
Circuit Description
The throttle position (TP) sensor circuit provides a voltage signal that changes relative to throttle blade angle. The signal voltage will vary from below 1 volt at closed throttle to about 4 volts at wide open throttle (WOT).
The TP signal is used by the powertrain control module (PCM) for fuel control and most of the PCM-controlled outputs. If the PCM detect a continuous open in the TP sensor or circuit, then a code P0123 will set. DTC P0123 is a type A code.
Conditions for Setting the DTC
- The ignition is ON.
- Throttle Position sensor signal voltage is greater than 4.78 volts for a total of 0.78 second over a 1.5 - second period.
Action Taken When the DTC Sets
- The PCM will illuminate the malfunction indicator lamp (MIL) the first time the fault is detected.
- The PCM will store conditions which were present when the DTC was set as Freeze Frame and in the Failure Records data.
- The PCM will use a default throttle position based on MAP and RPM.
Conditions for Clearing the MIL/DTC
- The PCM will turn the MIL OFF on the third consecutive trip cycle during which the diagnostic has been run and the fault condition is no longer present.
- A history Diagnostic Trouble Code P0123 will clear after 40 consecutive warm-up cycles have occurred without a fault.
- Diagnostic Trouble Code P0123 can be cleared by using the Scan Tool's "Clear Info" function.
Diagnostic Aids
Check for the following conditions:
- Poor connection at PCM - Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal-to-wire connection.
- The TP sensor shares a 5 Volt reference with the MAP sensor and Fuel Pressure sensor.
If these codes are also set, it could indicate a problem with the 5 Volt reference circuit or components itself.
- The TP sensor share a ground with the MAP and the Fuel Pressure sensor.
- Damaged harness - Inspect the wiring harness for damage, shorts to ground, shorts to battery positive and open circuits. If the harness appears to be OK, observe the Throttle Position sensor display on the Tech 2 while moving connectors and wiring harnesses related to the TP sensor. A change in the display will indicate the location of the fault.
- Faulty Throttle Position sensor - With the ignition key ON engine OFF observe the TP sensor display on the Tech 2 while slowly depressing the accelerator to wide open throttle. If a voltage over 4.88 volts is seen at any point in normal accelerator travel, replace the TP sensor.
If Diagnostic Trouble Code P0123 cannot be duplicated, the information included in the Failure Records data can be useful in determining vehicle mileage since the Diagnostic Trouble Code was last set. If it is determined that the Diagnostic Trouble Code occurs intermittently, performing the Diagnostic Trouble Code P1121 Diagnostic Chart may isolate the cause of the fault.
Steps 1 - 3:
Steps 4 - 7:
Steps 8 - 11:
Step 12:
Test Description
Number(s) below refer to the step number(s) on the Diagnostic Chart:
7. Components that share the TP sensor 5 volt reference circuit include the following devices:
- EGR valve
- Fuel Tank Pressure sensor
- MAP sensor
Disconnect the component while observing the Throttle Position sensor display on the Tech 2. If the reading changes drastically when this component is disconnected, replace the component that affected the reading.