P0121

DESCRIPTION
The Throttle Position sensor mounts on the side of the throttle body and is connected to the throttle valve shaft. The TPS is a variable resistor (potentiometer) whose resistance changes according to throttle valve shaft position. During acceleration, the TPS resistance decreases; during deceleration, the TPS resistance increases.

The Engine Control Module (ECM) applies a reference voltage to the TPS and then measures the voltage that is present on the TPS signal circuit. The ECM uses the TPS signal to adjust timing and injector pulse width. The TPS signal along with the MAF sensor signal is used by the ECM to calculate engine load.

FAILURE CONDITIONS
The ECM will set P0121 and the Malfunction Indicator Lamp (MIL) will turn on if the engine load indicated by the Throttle Position (TP) sensor and the Mass Air Flow (MAF) sensor are different. This code indicates that the throttle position and air flow readings by the TP and MAF sensor, or ECM, do not result in the expected engine load value.

The ECM will set P0122 and the Malfunction Indicator Lamp (MIL) will turn on if the throttle angle is reported as less than 2.1 degrees for more than 0.2 seconds during 2-driving cycles. This code indicates an unusually low throttle position angle being read by the TP sensor or ECM.

The ECM will set P0123 and the Malfunction Indicator Lamp (MIL) will turn on if the throttle angle is reported as greater than 105.4 degrees for 0.2 seconds during 2-driving cycles. This code indicates an unusually high throttle position angle being read by the TP sensor or ECM.

NOTE: The standard resistance value between terminals 1 and 3 of the throttle position sensor is 1600 - 2500 ohms.

Circuit Diagram:

Test Procedure Part 1:

Test Procedure Part 2:

Test Procedure Part 3: