P0121

DTC P0121

Circuit Description

The powertrain control module (PCM) uses the following information to calculate an expected airflow rate:

* The throttle position (TP)
* The barometric pressure (BARO)
* The manifold absolute pressure (MAP)
* The intake air temperature (IAT)
* The mass air flow (MAF)
* The engine RPM

If the PCM detects the airflow rate is more than expected, DTC P0121 sets.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC P0121 Throttle Position (TP) Sensor 1 Performance

Conditions for Running the DTC

* DTCs P0641, P0651, P1516, P2101, P2119, P2176 are not set.
* The engine is running and the engine speed is more than 600 RPM.
* DTC P0121 runs continuously when the above conditions are met.

Conditions for Setting the DTC

The PCM detects that the calculated airflow rate is more than expected for more than 10 seconds.

Action Taken When the DTC Sets

* The control module illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails.
* The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame and/or the Failure Records.
* The control module commands the TAC system to operate in the Reduced Engine Power mode.
* A message center or an indicator displays Reduced Engine Power.
* Under certain conditions the control module commands the engine OFF.

Conditions for Clearing the MIL/DTC

* The PCM will turn OFF the malfunction indicator lamp (MIL) during the third consecutive trip in which the diagnostic has 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.

Test Description

Step 1 - Step 7:

Step 8 - Step 10:

The numbers below refer to the step numbers on the diagnostic table.
5. This step will determine if the MAP sensor voltage is within the proper range at idle.
6. This step will determine if the MAP sensor responds properly to the change in manifold pressure.
9. When the PCM detects a condition within the ETC system other DTCs may set due to the many redundant tests run continuously on this system. Locating and repairing one individual condition may correct more than one DTC. Keep this in mind when reviewing captured DTC info.