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 circuits:
- A 5-volt reference circuit
- A low reference circuit
- A TP sensor 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 in order to determine if the predicted operating range of the TP sensor is correct. If the PCM detects 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 Performance

CONDITIONS FOR RUNNING THE DTC
- DTCs P0101, P0102, P0103, P0106, P0107, P0108, P0120, P0220, P0506, P0507 are not set.
- The engine is running for more than 2 minutes.
- The engine coolant temperature (ECT) is more than 60°C (140°F).
- The MAP is less than 43 kPa for a TP sensor skewed high test.
- The MAP is more than 68 kPa for a TP sensor skewed low test.
- The MAP is steady for 1 second or more.
- The TP does not vary more than 1.5 percent for 1 second or more.
- DTC P0121 runs continuously when the above conditions are met.

CONDITIONS FOR SETTING THE DTC
- The PCM detects that the TP sensor voltage is more than a predicted value when the MAP is less than 43 kPa.ORThe PCM detects that the TP sensor voltage is less than a predicted value when the MAP is more than 68 kPa.
- The above condition is met for 15 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 malfunction indicator lamp (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 - 7:

Steps 8 - 12:

Steps 13 - 21:

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