P0121
CIRCUIT DESCRIPTIONThe 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 three circuits:
^ A 5-volt reference circuit
^ A low reference circuit
^ A signal circuit
The PCM provides the TP sensor with a 5-volt reference circuit and a 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 greater than 4 volts through the TP sensor signal circuit. When the conditions for running this DTC are met the PCM will use the MAP sensor to determine if the predicted operating range of the TP sensor is correct. A skewed MAP sensor may cause this DTC to set and should be tested for proper operation if the TP sensor is determined to be operating properly and this DTC continues to set.
CONDITIONS FOR RUNNING THE DTC
^ DTCs P0106, P0107, P0108, P0122, P0123, P1106, P1107, P1121, or P1122 are not set.
^ The engine is running for greater than 2 minutes.
^ The engine coolant temperature (ECT) is greater than 60°C (1400°F).
^ The MAP reading is less than 55 kPa for a TP sensor skewed high test.
^ The MAP reading is greater than 65 kPa for a TP sensor skewed low test.
^ The MAP is steady for 1 second or more.
CONDITIONS FOR SETTING THE DTC
^ The TP sensor reading is greater than a predicted value when the MAP is below 55 kPa.
^ The TP sensor reading is less than a predicted value when the MAP is above 65 kPa.
^ The above conditions are present 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.
DIAGNOSTIC AIDS
Inspect for the following conditions:
^ A skewed MAP signal-A skewed MAP signal may cause the PCM to incorrectly determine the TP sensor is out of range. Inspect for an unusually low or high MAP reading.
^ If the DTC is determined to be intermittent or the TP sensor system is still suspect, refer to DTC P1121 and/or Intermittent Conditions. P1121
TEST
