Diagnostic code P0201 OBDII indicates that the Powertrain Control Module (PCM) has detected an injector fault. The problem may also be in one of the cables leading to the injector.
The injector is monitored by the Powertrain Control Module (PCM) and when activated, the voltage should be low or close to 0. Conversely, when the injector is turned off, the voltage the PCM expects to see should be a high voltage or close to the battery voltage. Likewise, the resistance of the circuit is monitored by the PCM. If the expected voltage is not observed in the conditions already mentioned both in the injector voltage and in its resistance, the DTC P0201 OBD2 is established.