What does code p2138 mean on the chevy impala?

When a Chevy Impala returns a P2138 trouble code, it means there is something happening that is stopping the throttle from opening and closing as it should. There are essentially two sensors in one assembly that create the accelerator pedal position sensor. Each of these sensors receives a low reference circuit and A5-volt reference circuit by the engine control module. It's also helpful to understand that the accelerator pedal position is used by the powertrain control module to determine how much torque is being requested at any given time. If the problem lies with the throttle body itseLFAnd not just the sensor, it will generally cost between $310 and $440. Labor makes up $70 to $90 of that total.