P0121

DTC P0121 THROTTLE/PEDAL POSITION SENSOR/SWITCH "A" CIRCUIT RANGE/PERFORMANCE PROBLEM

HINT: This DTC relates to the Throttle Position (TP) sensor.

CIRCUIT DESCRIPTION

DTC Detection Conditions:

The TP sensor is mounted on the throttle body and detects the throttle valve opening angle.

When the throttle valve is fully closed, the sensor transmits a signal voltage of approximately 0.3 to 1.0 V to terminal VTA of the ECM. This signal voltage increases in proportion to the opening angle of the throttle valve, reaching approximately 3.2 to 4.9 when the throttle valve is fully open.

The ECM determines the vehicle driving conditions from these signals and uses this information in functions such as air-fuel ratio correction, power increase correction and fuel-cut control.

MONITOR DESCRIPTION

Monitor Strategy:

Typical Enabling Condition:

Typical Malfunction Thresholds:

Component Operating Range:

The resistance of the TP sensor varies in accordance with the throttle valve opening angle. The ECM transmits a standardized reference voltage to the +:VC terminal of the TP sensor and calculates the throttle valve opening angle based on the voltage received from the Signal:VTA terminal of the sensor.

When the throttle valve is near the fully closed position, the output voltage of the TP sensor is low. When it is near the fully open position, the output voltage is high.

The ECM monitors the indicated throttle valve opening angle during stop-and-go driving conditions. If the indicated angle (or voltage) in the closed throttle valve position is outside the specified range, the ECM interprets this as a malfunction in the TP sensor and sets the DTC.

HINT: When this DTC is set, the ECM enters fail-safe mode. During fail-safe mode, the ECM cuts fuel intermittently. Fail-safe mode continues until a pass condition is detected and the ignition switch is turned to OFF.

Stop-and-go is defined as follows:
Stop indicates a vehicle speed of 0 mph (0 km/h). Go indicates a vehicle speed of 18.6 mph (30 km/h).

Step 1:

INSPECTION PROCEDURE

HINT: Read freeze frame data using a hand-held tester or OBD II scan tool. Freeze frame data record the engine condition when malfunctions are detected. When troubleshooting, freeze frame data can help determine if the vehicle was moving or stationary, if the engine was warmed up or not, if the air-fuel ratio was lean or rich, and other data, from the time the malfunction occurred.