What does p2138 code mean on the chevy malibu?

On the Chevrolet Malibu (and other OBD-II equipped vehicles), diagnostic trouble code (DTC) P2138 indicates an issue with the throttle position sensor. The actual code readout will be "Throttle/Pedal Position Sensor/Switch D/E Voltage Correlation", which essentially means that the engine control module (ECM) has detected issues in the D and/or E circuits of the TPS. If you see the code, it's possible that you'll also have problems with stalling, failing to start, or poor acceleration. The most likely (but not only) cause of the DTC is a failed throttle position sensor, so be aware that replacing it may not fix your issue. You may need to also replace the wiring, the throttle body assembly, or even the entire engine control module, if that's where your diagnosis takes you.