P0121

DTC P0121

CIRCUIT DESCRIPTION
The throttle position (TP) sensor is used by the powertrain control module (PCM) to determine the throttle plate angle for various engine management systems. The TP sensor is a potentiometer type sensor with the following three circuits:
- A 5-volt reference circuit
- A low reference circuit
- A signal circuit

The PCM provides the TP sensor with 5 volts on the 5-volt reference circuit and a ground on the low reference circuit. Rotation of the TP sensor rotor from the closed throttle position to the wide open throttle (WOT) position provides the PCM with a signal voltage from less than 1 volt to more than 4 volts through the TP sensor signal circuit. When the conditions for running this DTC are met, the PCM will use the manifold absolute pressure (MAP) sensor to determine if the predicted operating range of the TP sensor is correct. If the PCM detects that the TP sensor voltage is out of the predicted range DTC P0121 sets.

DTC DESCRIPTOR
This diagnostic procedure supports the following DTC:
DTC P0121 Throttle Position (TP) Sensor Replacement

CONDITIONS FOR RUNNING THE DTC
- DTCs P0107, P0108, P0122, P0123, P0506, P0507 are not set.
- The engine is running for more than 2 minutes.
- The ECT Sensor parameter is more than 75°C (167°F).
- The MAP Sensor parameter is less than 50 kPa for a TP sensor skewed high test.
- The MAP Sensor parameter is more than 70 kPa for a TP sensor skewed low test.
- The MAP Sensor parameter does not change more than 5 kPa for more than 5 seconds.
- The IAC Position parameter is between 0-130 counts.
- DTC P0121 runs continuously once the above conditions are met.

CONDITIONS FOR SETTING THE DTC
The TP sensor voltage is more or less than a predicted value for more than 10 seconds.

ACTION TAKEN WHEN THE DTC SETS
- The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
- The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

CONDITIONS FOR CLEARING THE MIL/DTC
- The control module turns OFF the MIL after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
- A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
- A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
- Clear the MIL and the DTC with a scan tool.

TEST DESCRIPTION

Steps 1-8:

Steps 9-13:

Steps 14-22:

The numbers below refer to the step numbers on the diagnostic table.
13. This step calculates the resistance in the 5-volt reference circuit.
14. This step calculates the resistance in the low reference circuit.