Circuit Description

Accelerator pedal position sensor is located on throttle body and uses 2 sensors which monitor accelerator position. Accelerator pedal position sensor delivers input signals to VPA and VPA2 terminals at Engine Control Module (ECM) in proportion to throttle opening. ECM uses input signals for controlling the throttle control motor. DTC is set when ECM determines voltage is out of range on VPA or VPA2 circuits between accelerator pedal position sensor and ECM. If DTC P1121 exists, ECM will turn off the power to throttle control motor and throttle valve is closed by the return spring. When this occurs, throttle valve is controlled by throttle cable connected to accelerator pedal. Possible cause is defective accelerator pedal position sensor.