What does it mean?
OBD II fault code P0245 is a generic trouble code that is defined as “Turbocharger (TC) wastegate regulating valve “A” – circuit low”, and is set when the PCM (Powertrain Control Module) detects an unexpectedly low voltage in the circuits of a turbochargers’ wastegate control actuator. Note that this code only applies to forced induction engines that use a purely electrically controlled actuator to open and close the turbocharger’s wastegate, or dump valve, as it is also known.
Depending on the application and turbocharger’s design a wastegate or dump valve can have to different functions, although both functions have the same objective, which is to regulate the pressure in the boost system. In practice, a wastegate can either allow excessive boost pressure to vent into the exhaust system, or it can be used to limit the amount of exhaust gas (which serves to drive the turbocharger) that enters the turbine side of the turbocharger.
In terms of operation, a wastegate is simply a kind of trapdoor in the turbocharger’s housing that allows excessive drive pressure to be vented into the exhaust. In designs that limit exhaust gas that enters the turbocharger, the limitation is used to limit the rotational speed of the compressor wheel as a means to control boost pressure.
By way of contrast, turbocharger designs that use boost pressure to control the wastegate keep the wastegate closed, which allows all the exhaust gas that exits the engine to pass through the turbine side of the turbocharger to drive the compressor wheel, meaning that boost pressure can increase unchecked. In the latter design, some boost pressure is diverted to act on a diaphragm in the actuator.
When boost pressure is sufficient to overcome the spring tension, the actuator pulls open the wastegate, which relieves the pressure of the exhaust gas in the turbine side, which in turn, reduces boost pressure because the pressure in the compressor side of the turbocharger exerts a braking force on the compressor wheel. While this system works reasonably well, it is very difficult to calibrate these designs to a point where boost pressure can be maintained within a very narrow range.
In practice, these systems/designs produce significant fluctuations in boost pressure, which ultimately affects engine performance and efficiency. Thus, to eliminate these fluctuations, modern boost control systems use advanced algorithms to calculate the speed of the turbine wheel at any given engine speed and throttle opening, this speed being the principal factor that determines boost pressure at any point in the engine’s operating range.
Therefore, by using the PCM to control the wastegate with an electronically controlled actuator to limit the amount of exhaust gas that can act on the turbine, the speed of the turbine can be controlled precisely, which translates into precise control of the boost pressure throughout the engine’s operating range.
For this system to work, however, the PCM needs to monitor all relevant parameters continuously, and if it detects an abnormally low voltage or current in any circuit in the boost control system, it will recognize that it cannot control the boost pressure effectively, and it will set code P0245 and illuminate a warning light as a result.