This diagnostic trouble code P0027 code Isuzu NRP exhaust valve control solenoid circuit (bank 1) (DTC) is a generic powertrain code, which means that it applies to OBD-II equipped vehicles, including but not limited to Toyota, VW, Ford, Dodge, Honda, Chevrolet, Hyundai, Audi, Acura, etc. Check the engine oil level to make sure engine oil capacity is sufficient. Since the actuators work on oil pressure, the proper amount of oil is critical to ensure proper operation of the VVT system. Dirty or contaminated fluid may cause buildup which can lead to failure of the control solenoid or the camshaft actuator. Control solenoid - The control solenoid for the camshaft can be checked for continuity using a Digital volt/ohm meter (DVOM) using the ohms function, by unplugging the solenoid wiring harness connector and checking the resistance of the solenoid with the (+) and (-) leads of the DVOM on each terminal. Ensure the internal resistance is within manufacturers specifications if available. The camshaft actuator is a mechanical device controlled by internal spring pressure and adjusted by oil supplied by the control solenoid. When no oil pressure is supplied, it will default to a "safe" position. Check timing chain/belt and components to ensure they are in proper working order and installed in the correct position on the camshaft gear. ECM/PCM  A graphing multimeter or oscilloscope tool is required to view the PWM signal to ensure proper operation of the ECM/PCM. To check the PWM signal, the positive (+) lead is tapped into the ground side of the control solenoid ( if supplied by constant voltage, ground controlled ) or the powered side of the control solenoid (if permanently grounded, positive control ) and the negative (-) lead is attached to a good known ground. If the PWM signal is not consistent with changes in engine RPM, there may be a problem with the ECM/PCM.