P0121

Diagnostic Chart (Part 1 Of 2):

Diagnostic Chart (Part 2 Of 2):

Refer to Engine Controls Schematic A/C Refrig Press, TP, MAP, ECT, IAT.

CIRCUIT DESCRIPTION
The Throttle Position (TP) sensor circuit provides a voltage signal that changes relative to the throttle blade angle. The signal voltage will vary from less than 1.0 volt at closed throttle to more than 4.0 volts at Wide Open Throttle (WOT).

When the Manifold Absolute Pressure (MAP) reading is less than 50 kPa, the diagnostic tests for a skewed high TP sensor. When the MAP reading is more than 70 kPa, the diagnostic tests for a skewed low TP sensor. If the Powertrain Control Module (PCM) detects an out of range condition, DTC P0121 will set. The diagnostic will not run when MAP is between 50 kPa and 70 kPa.

CONDITIONS FOR RUNNING THE DTC
^ There are no active TP sensor circuit or Manifold Absolute Pressure (MAP) sensor Diagnostic Trouble Codes (DTCs).
^ The engine is running for more than 2 minutes
^ The ECT sensor temperature is more than 75°C (167°F).
^ The MAP reading is less than 50 kPa for a TP sensor that is skewed high.
^ The MAP reading is more than 70 kPa for a TP sensor that is skewed low.
^ The MAP is steady for 5 seconds or more.

CONDITIONS FOR SETTING THE DTC
^ The TP sensor reading is more than the predicted value when the MAP is less than 50 kPa.
^ The TP sensor reading is less than the predicted value when the MAP is more than 70 kPa.
^ The above conditions are present for 10 seconds.

ACTION TAKEN WHEN THE DTC SETS
^ The PCM will illuminate the Malfunction Indicator Lamp (MIL) during the second consecutive trip in which the diagnostic has been run and failed.
^ If equipped with traction control, the PCM will command the Electronic Brake And Traction Control Module (EBTCM) via the serial data circuit to turn OFF traction control, and the EBTCM will illuminate the TRACTION OFF lamp.
^ The PCM will store conditions which were present when the DTC set as Freeze Frame and Failure Records data.

CONDITIONS FOR CLEARING THE MIL/DTC
^ The PCM will turn OFF the MIL during the third consecutive trip in which the diagnostic has been run and passed.
^ The History DTC will clear after 40 consecutive warm-up cycles have occurred without a malfunction.
^ The DTC can be cleared by using a scan tool.

DIAGNOSTIC AIDS
Inspect for the following conditions:
^ A stuck or skewed MAP signal or a faulty MAP sensor.
^ A skewed MAP signal may cause the PCM to incorrectly determine the TP sensor is out of range. Test for an unusually low or high MAP reading. This condition can cause DTC P0121 to set. Refer to MAP Sensor Circuit Diagnosis. Component Tests and General Diagnostics

IMPORTANT: Remove any debris from the connector surfaces before servicing a component. Inspect the connector gaskets when diagnosing or replacing a component. Ensure that the gaskets are installed correctly. The gaskets prevent contaminate intrusion.

^ Poor terminal connection - Inspect the harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and faulty terminal to wire connection. Use a corresponding mating terminal to test for proper tension.
^ Damaged harness - Inspect the wiring harness for damage. If the harness inspection does not reveal a problem, observe the display on the scan tool while moving connectors and wiring harnesses related to the sensor. A change in the scan tool display may indicate the location of the fault.
^ PCM and engine grounds for clean and secure connections

If the DTC is determined to be intermittent, reviewing the Failure Records can be useful in determining when the DTC was last set.

TEST DESCRIPTION
The numbers below refer to the step numbers on the diagnostic table.
11. This vehicle is equipped with a PCM which utilizes an Electrically Erasable Programmable Read Only Memory (EEPROM). When the PCM is being replaced, the new PCM must be programmed.