P0122
DTC P0122 TP Sensor Circuit Low 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 lower 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 less than 0.25 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 throttle position in volts. The TP should read about 0.45 - 0.85 volts with the throttle closed and the ignition ON or at idle. The voltage should increase at a steady rate as the throttle is moved toward Wide Open Throttle (WOT).
An open or short to ground in the 5 volt reference circuit or the TP sensor signal circuit results in a DTC P0122.
Refer to the Symptoms.
Scan the TP sensor signal while depressing the accelerator pedal with the engine stopped and the ignition ON. The display should vary from below 1.25 volts (1250 mV) when throttle was closed, to over 4.5 volts (4500 mV) when throttle is held at the Wide Open Throttle (WOT) position.
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 - 7:
Steps 8 - 15:
Steps 16 - 20:
Test Description
The numbers below refer to the step numbers on the diagnostic table.
2. If the TP signal measures less than 0.25 volt, then the low voltage condition exists.
3. If the VCM recognizes the high signal voltage, the VCM and the wiring are okay.
7. The VCM terminals C3 12 and C3 27 are spliced together inside the VCM. When checking the 5 volt reference circuit for a short to ground, both the 5 volt reference circuits and all the components on the 5 volt reference circuits must be checked.