P0123

CIRCUIT DESCRIPTION




The DTC P0123 Throttle Position (TP) Sensor Circuit High Voltage diagnostic monitors the TP sensor signal. The TP sensor is a potentiometer whose resistance value changes along with the throttle valve position. The powertrain control module (PCM) provides a 5-volt reference voltage to the TP sensor. The PCM reads the voltage across the TP sensor and uses the voltage to calculate the percentage of throttle valve opening. The TP sensor resistance decreases as the throttle valve opening increases. When the TP sensor resistance decreases the voltage being monitored by the PCM increases. The TP sensor resistance increases when the throttle valve opening decreases, therefore the voltage being monitored by the PCM will decrease.

CONDITIONS FOR RUNNING THE DTC
The ignition is ON or the engine is running.

CONDITIONS FOR SETTING THE DTC
- A high TP sensor voltage is indicated at the PCM.
- The above condition is present for at least 5 seconds.

ACTION TAKEN WHEN THE DTC SETS
- The PCM illuminates the malfunction indicator lamp (MIL).
- The PCM records the operating conditions at the time the diagnostic fails. This information is stored in the Freeze Frame buffer.
- The PCM enters the Fail-safe mode and assumes the engine throttle valve angle is 24.5 degrees (M/T) or 0 degrees (4 speed A/T).

CONDITIONS FOR CLEARING THE MIL/DTC
- The MIL turns off after 3 consecutively passing cycles without a fault present.
- A history DTC will clear after 40 consecutive warm-up cycles without a fault.
- Perform the scan tool clear DTC Information function in order to clear the DTC.

TEST DESCRIPTION

Steps 1-3:

Steps 4-5:

Steps 5-9:

Steps 10-13:

The numbers below refer to the step numbers in the diagnostic table.
1. The Diagnostic System Check-Computers and Control Systems prompts the technician to complete some basic checks and store the Freeze Frame data on the scan tool if applicable. This creates an electronic copy of the data taken when the fault occurred. The information is then stored in the scan tool for later reference.
2. If a DTC P2027 is also set there is a fault in the sensor ground circuit or the PCM.
3. A typical TP sensor reading on the scan tool will be near 0.73 volts with a 0 percent throttle angle.
6. A typical TP sensor reading on the scan tool will be near 0.73 volts with a 0 percent throttle angle.
12. Clearing the DTCs by removing the DOME fuse also clears the PCM long term memory. Using the scan tool to clear DTCs leaves the long term memory active. DTC emitting diagnostics may not run to completion as expected unless the long term memory is cleared. Removal of the DOME fuse also clears the time display of the radio. The DTC P0123 diagnostic can be monitored on the scan tool under the Not Ran Since Code Cleared selection in the DTC Information menu. If DTC P0123 appears in the Not Ran Since Code Cleared list, the P0123 diagnostic has not yet run. When DTC P0123 does not appear in the Not Ran Since Code Cleared list, the P0123 diagnostic has run. If the MIL is NOT illuminated and there is no Pending DTC Status in DTC Information, the P0123 diagnostic has passed. The DTCs MUST be cleared in order to view the Current Status of the Not Ran Since Code Cleared list. The DTC Information screen must be checked for Current or Pending status in order to determine the outcome of the diagnostic test involved.