P0123

DTC P0123 TP Sensor Circuit High Voltage




Circuit Description
The Throttle Position (TP) sensor is a three wire potentiometer using a 5 volt reference, a ground and a signal circuit. The TP sensor signal circuit detects voltage changes on the potentiometer (variable resistor) as the throttle angle changes. The TP sensor signal voltage varies from 0.6 volts at idle to approximately 4.6 volts at wide open throttle. The TP sensor is one of the primary inputs to the VCM. Its input is important to most engine and transmission functions.

This DTC is designed to detect a TP sensor signal voltage higher than the possible operating range of a normally functioning TP sensor.

Conditions for Running the DTC
The engine is running.

Conditions for Setting the DTC
The TP sensor signal voltage is greater than 4.7 volts for 1 second.

Action Taken When the DTC Sets
- The VCM illuminates the MIL (Malfunction Indicator Lamp) if a failure is detected during 2 consecutive key cycles.
- The VCM will set the DTC and records the operating conditions at the time the diagnostic fails. The VCM stores the failure information in the scan tools Freeze Frame and/or the Failure Records.

Conditions for Clearing the MIL/DTC
- The VCM turns OFF the MIL after 3 consecutive drive trips when the test has Run and Passed.
- A history DTC will clear if no fault conditions have been detected for 40 warm-up cycles (coolant temperature has risen 22 °C (40 °F) from the startup coolant temperature and the engine coolant temperature is more than 70 °C (158 °F) during the same ignition cycle).
- Use the scan tool Clear Information function.

Diagnostic Aids
The scan tool reads the throttle position in volts. The scan tool should read about 0.45 - 0.85 volt with the throttle closed and the ignition switch turned ON or at idle. The voltage should increase at a steady rate as the throttle is moved toward the Wide Open Throttle (WOT).

Also some scan tools will read the throttle angle. 0% = closed throttle. 100% = WOT.

Scan the TP sensor while depressing the accelerator pedal with the engine turned OFF and the ignition turned on. The display should vary from below the 1.25 volts (1250 mV) when the throttle was closed to over 4.5 volts (4500 mV) when the throttle is held at WOT position.

This DTC will result if the TP ground circuit is open or the TP signal circuit is shorted to the voltage.

Refer to the Symptoms.

An intermittent may be caused by any of the following conditions:
- A poor connection
- Rubbed through wire insulation
- A broken wire inside the insulation

Thoroughly check any circuitry that is suspected of causing the intermittent complaint. Refer to Intermittents and Poor Connections Diagnosis.

If a repair is necessary, then refer to Wiring Repairs or Connector Repairs.

Steps 1 - 2:

Steps 3 - 8:

Steps 9 - 14:

Steps 15 - 18:

Test Description
The numbers below refer to the step numbers in the diagnostic table.
2. If the TP signal measures greater than 4.8 volts, then the conditions exists.
3. With the TP sensor disconnected, and if the VCM and the wiring are okay, the TP signal should go low.
6. This step checks the EGR valve for a back feed into the 5 volt reference circuit.