What does it mean?
A properly running engine is essentially the precise timing of gasoline-fueled explosions. Depending on engine speed (RPM) and load the engine control unit (ECU) controls the timing and amount of fuel injection, timing of spark ignition, and in the case of engines with variable valve timing (VVT), intake- and exhaust-valve timing adjustments. The two main timing and position sensors used by the ECU are the crankshaft position sensor (often CKP) and camshaft position sensor (often CMP).
If there are two banks on a VVT-equipped engine, then there will be two camshaft position sensors. The camshaft position sensor reacts to a toothed wheel on the camshaft, which gives the ECU constant information on its speed and position. Of course, the CMP is located on the engine, usually somewhere on the cylinder head, so it transmits CMP data to the ECU using wires.
If the ECU detects a range / performance problem with the CMP signal, it will set DTC P0341 or DTC P0346 – Camshaft Position Sensor Circuit Malfunction. If your engine has only one CMP, such as an inline-four-cylinder, the only CMP code available is for Bank 1, P0341. On the other hand, V6 or V8 engines have two banks, Bank 1 and Bank 2, and would therefore have two CMPs, so DTC P0346 would refer to Bank 2.
Sensor A indicates that the malfunction is occurring with the camshaft position sensor circuit that pertains to the intake camshaft. Sensor B codes pertain to the exhaust camshaft.