P0121

Diagnostic Chart 1 Of 2:

Diagnostic Chart 2 Of 2:

Schematic:

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 MAP reading is less than 50 kPa, the diagnostic checks for a skewed high TP Sensor. When the MAP reading is above 70 kPa, the diagnostic checks for a skewed low TP sensor. If the PCM detects an out of range condition, DTC P0121 will be set. The diagnostic will not run between 50 kPa and 70 kPa.

CONDITIONS FOR RUNNING THE DTC
^ There is no active TP sensor circuit or MAP sensor DTC.
^ The engine is running.
^ The ECT Sensor temperature above 70°C (158°F).
^ The MAP reading is below 50 kPa.
^ The MAP reading is above 70 kPa.
^ The MAP steady for 5 seconds or more.

CONDITIONS FOR SETTING THE DTC
^ The TP Sensor reading is above the predicted value when the MAP is below 50 kPa.
^ The TP Sensor reading is below the predicted value when the MAP is above 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 test has been run and failed.
^ 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 the MIL OFF 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 the scan tool.

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

^ A poor connection at the PCM and at the TP sensor.
Inspect the harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal-to-wire connections. Use a corresponding mating terminal to test for proper tension. Refer to Testing for Intermittent and Poor Connections, Repairing Connector Terminals and Connector Repairs.
^ A damaged harness
Inspect the wiring harness for damage. If the harness appears to be OK, observe the TP sensor display on the scan tool while moving the connectors and the wiring harnesses that are related to the sensor. A change in the display will indicate the location of the fault. Refer to Wiring Repairs in Diagrams.

If DTC P0121 cannot be duplicated, the information included in the Failure Records data can be useful in determining vehicle mileage since the DTC was last set. If it is determined that the DTC occurs intermittently, performing the DTC P1121 Throttle Position (TP) Sensor Circuit Intermittent High Voltage diagnostic may isolate the cause of the fault. P1121

TEST DESCRIPTION
The number below refers to the step number on the Diagnostic Table:
12. 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.