P0123

Diagnostic Chart (Part 1 Of 2):

Diagnostic Chart (Part 2 Of 2):

Schematic:

CIRCUIT DESCRIPTION
The Throttle Position (TP) sensor is a potentiometer. The TP sensor is mounted to the left side of the throttle body. The TP sensor provides a voltage signal that changes relative to throttle blade angle. This signal voltage is one of the most important inputs used by the Powertrain Control Module (PCM). The TP sensor has a 5.0 volt reference, a ground, and a signal circuit.

TP sensor signal voltage should be near 0.6 volt at idle. The TP sensor voltage should increase to above 4.0 volts at Wide Open Throttle (WOT).

When the PCM senses a signal voltage higher than the normal operating range of the sensor, this Diagnostic Trouble Code (DTC) sets.

CONDITIONS FOR RUNNING THE DTC
The ignition switch is in the ON position or the engine is operating.

CONDITIONS FOR SETTING THE DTC
^ The TP sensor signal voltage is more than 4.75 volts.
^ The condition is present for 10 seconds.

ACTION TAKEN WHEN THE DTC SETS
^ The PCM illuminates the Malfunction Indicator Lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
^ The PCM records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the PCM stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the PCM records the operating conditions at the time of the failure. The PCM writes the conditions to the Freeze Frame and updates the Failure Records.
^ The PCM uses a default TP sensor value.
^ The transmission line pressure increases.
^ Firmer transmission shifts

CONDITIONS FOR CLEARING THE MIL/DTC
^ The PCM turns OFF the Malfunction Indicator Lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
^ A last test failed, or current DTC, clears when the diagnostic runs and does not fail.
^ A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
^ Use a scan tool in order to clear the MIL and the DTC.

DIAGNOSTIC AIDS

IMPORTANT: Remove any debris from the PCM connector surfaces before servicing the PCM. Inspect the PCM connector gaskets when diagnosing or replacing the PCM. Ensure that the gaskets are installed correctly. The gaskets prevent water intrusion into the PCM.

^ The following may cause an intermittent:
- Mis-routed harness
- Rubbed through wire insulation
- Broken wire inside the insulation
^ The PCM 5.0 volt reference circuits are internally connected within the PCM. If all the TP sensor circuits are OK, inspect the fuel tank pressure sensor for malfunctions. If DTC P1639 sets at the same time, this indicates that the 5.0 volt reference circuit is either shorted to a ground or shorted to a voltage.
^ If it is determined that the DTC occurs intermittently, performing the DTC P1121 diagnostic table may isolate the cause of the fault.
^ For an intermittent, refer to Symptoms. Symptom Related Diagnostic Procedures

TEST DESCRIPTION
The numbers below refer to the step numbers on the diagnostic table.
2. If DTC P1639 sets at the same time, this indicates that the 5 volt reference circuit is shorted to a ground. The 5 volt reference circuit is internally connected within the PCM.
3. This step checks if the fault is present.
4. Using Freeze Frame and Failure Records data may aid in locating an intermittent condition. If you cannot duplicated the DTC, the information included in the Freeze Frame and Failure Records data can help determine how many miles since the DTC set. The Fail Counter and Pass Counter can also help determine how many ignition cycles the diagnostic reported a pass or a fail. Operate vehicle within the same Freeze Frame conditions such as RPM, load, vehicle speed, temperature, etc. that you observed. This will isolate when the DTC failed.
5. This step determines if the signal circuit is shorted to a voltage.
6. This checks whether the ground circuit is available to the TP sensor. Check for poor electrical connections at the TP sensor.