What does it mean?
Code P0033 is a generic powertrain code that is used in both turbocharger and supercharger applications. When exhaust pressure builds up at the turbocharger/supercharger inlet, a pressure outlet hose on the turbocharger or supercharger directs excess pressure to the wastegate for release. On some boost solenoids, there may also be a vent to atmosphere or a bypass directly into the intake.
The bypass valve or boost solenoid actuates the wastegate at a certain pressure, allowing boost pressure to remain within the set allowances for the vehicle. It is controlled by the engine/powertrain control module (PCM). The boost solenoid or bypass valve is normally in the closed position. When pressure builds to the vehicle’s boost parameters, the solenoid switches, and the wastegate can be actuated to release pressure.
Should the solenoid fail to switch, excess pressure can cause turbocharger or engine damage from excess boost. However, if the solenoid remains in the open position, the turbocharger/supercharger’s inlet pressure will be insufficient to maintain proper boost for engine performance. DTC P0033 will be set in the PCM. Note: “Circuit Malfunction” indicates that there is a malfunction in the control circuit, as opposed to a fault in a sensor or other component.
With “Circuit Malfunction” codes, replacement of sensors and components in the affected circuit will almost never resolve the problem, since as the code suggests, the trouble is in the circuit . This distinction between “circuit” and “sensor/component” is a great help to anyone trying to diagnose a circuit malfunction code, since it narrows the list of possible causes down considerably.
The causes of “Circuit Malfunction” codes are much the same as those for “Open Circuits” i.e., broken wiring, poor connections across electrical connectors or previously repaired wiring, loss of ground that prevents current flow, blown fuses, defective relays, faulty switches, or any of a host of other issues and problems that prevents a flow of current through wiring. Issues like high/low/intermittent voltages can set a “Circuit Malfunction” code on some applications.
Moreover, “Circuit Malfunction” codes could also indicate a problem with negative current control / flow, as well as issues with failed or failing PCM’s (Powertrain Control Modules), although control module failure is a rare event.