P0121
DTC P0121 Throttle Position Sensor (TPS) Rationality CheckWiring Diagram:
Circuit Description
The aim of the MTIA (Main Throttle Idle Actuator) is to control the idle speed with the throttle body itself. The throttle is motorized for low opening angle (0, 18 °). The characteristics of the airflow are not the same for low and high opening angles. As a matter of fact, the gradient of the mass air flow function of TPS is lower for small angles that permits to be more precise during the idle speed control. Out of idle speed the throttle is actuated mechanically by a classical bowden cable.
The Throttle position sensor (TPS) provides a voltage signal that changes in relation to the throttle place angle. The signal voltage will vary from about 4.15 ~ 4.75 V at idles to about 0.3 ~ 1.05 V at wide-open throttle. The TPS is on of the most important inputs used by the ECM for fuel control and other functions such as idle, wide open throttle, deceleration enrichment, and acceleration enrichment.
Conditions for Setting the DTC
- Engine speed is between 1,000 rpm and 3,500 rpm.
- Relative engine load is between 0.3 and 0.7
- Engine load stable.
- Vehicle is operated in closed loop condition.
- No relevant DTCs are set
- The TPS signal indicates a value other than expected.
Action Taken When the DTC Sets
- The Malfunction Indicator Lamp (MIL) will illuminate.
- The ECM will record operating conditions at the time the diagnostic fail. This information will be stored in the Freeze Frame and Failure Records buffers.
- A history DTC is stored.
Conditions for Clearing the MIL/DTC
- The MIL will turn off at the end of three (3) consecutive validation cycles in which the diagnostic runs without a fault.
- A history DTC will clear after 40 warm up cycles without a fault.
- DTC(s) can be cleared by using the scan tool.
Diagnostic Aids
If the DTC P0121 cannot be duplicated, the information included in the Freeze Frame data can be useful. Use the scan tool DTC information data to determine the status of the DTC.
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Step 11 - 15:
DTC P0121 - Throttle Position Sensor (TPS) Rationality Check