DTC P1121: Throttle Position (TP) Sensor Signal Lower Than Expected: General Description

The throttle position (TP) sensor detects the position of the throttle valve. When the throttle valve is open (low-vacuum), the manifold absolute pressure (MAP) sensor outputs a high MAP value, and when the throttle valve is closed (high-vacuum), it outputs a low MAP value.

If the TP sensor detects a throttle position that is less than the set value when the MAP sensor outputs a higher MAP value (higher pressure) than the set value, a malfunction is detected and a DTC is stored.