The DTC P0033 OBDII code is stored because the PCM (Powertrain Control Module) gets an atypical input signal from the turbocharger bypass valve control circuit. This signal is not in the manufacturer’s specifications.
The PCM is in charge of the turbocharger bypass valve control. Sometimes it is commanded by a boost controller. Regardless of the case, the PCM calculates the input data from various turbocharger sensors in addition to the engine control. It determines the necessary position for the turbocharger bypass valve. It should be noted that the valve electronically regulates the boost pressure before it enters the intake manifold of the engine.
A small electronic motor is used to activate the valve. Then, the engine receives voltage or ground output signals from either the boost controller or the PCM. The signal wire from the turbocharger control circuit allows the PCM to monitor the system voltage. If a voltage is not within a predetermined range, the Check Engine light turns on along with this code. It should be noted that it is necessary to solve this code because there could be excessive boost pressure in the turbocharger.