What does P1390 code mean?

The P1390 code is a generic diagnostic trouble code (DTC) that indicates a problem with the camshaft position sensor circuit or its correlation with the crankshaft position sensor. It typically suggests that the engine control module (ECM) has detected an inconsistency in the timing or position of the camshaft compared to the crankshaft. This issue can lead to poor engine performance, misfires, or difficulty starting the engine. It's important to diagnose the specific cause, which may involve checking wiring, connectors, or the sensors themselves.