Technical Description of OBD-II Trouble Code
Turbocharger/Supercharger Turbine Overspeed
What is the meaning of this code?
This diagnostic trouble code (DTC) is a generic powertrain code that applies to OBD-II equipped vehicles (Dodge, Ram, Ford, GMC, Chevrolet, VW, Toyota, etc.). Although it is a generic code, the specific repair steps may vary depending on the make and model of the vehicle.
If you encounter a code P0049 in an OBD-II equipped vehicle, it means that the powertrain control module (PCM) has detected an overspeed condition in the turbocharger or supercharger turbine. This code could be caused by a mechanical or electrical malfunction in the forced air induction (FAI) system.
Turbochargers and superchargers are both used as forced air induction systems to increase engine performance. They draw in ambient air, compress it, and force it into the engine combustion chambers. The main difference between a turbocharger and a supercharger is how they are driven. A supercharger is driven by a belt connected to the engine crankshaft, while a turbocharger is driven by engine exhaust. To further cool and densify the introduced air, FAI systems often use an intercooler or may utilize methanol or cold water injection.
The boost controller is typically integrated into the PCM. The PCM calculates data from engine and transmission sensors to determine the required boost pressure for optimal engine performance. It monitors the actual boost pressure using one or more boost pressure sensors and compares it with the desired boost pressure. If the actual boost pressure exceeds the desired level, the PCM activates bypass control valves and/or blow-off valves to prevent an overboost condition.
Most bypass control valves and blow-off valves are electronically actuated. Before diagnosing a code P0049, it is recommended to consult a reliable vehicle information source for information specific to the forced air induction control system of your vehicle, such as All Data DIY.
If the PCM detects boost pressure higher than the programmed limit, it will store a code P0049 and may illuminate the malfunction indicator lamp (MIL).
Related turbo/supercharger engine trouble codes:
Symptoms & Severity
A genuine turbocharger/supercharger overboost condition could result in severe damage to the FAI device and/or engine. Therefore, a stored code P0049 should be considered severe.
Symptoms of a P0049 code may include:
Causes
Potential causes for this code to be set are:
Diagnostic and Repair Procedures
A good starting point is to check for any technical service bulletins (TSB) specific to your vehicle. There may be a known issue with a known fix provided by the manufacturer, which can save time and money during diagnosis.
To diagnose a code P0049, you will need a diagnostic scanner, a digital volt/ohmmeter (DVOM), a reliable vehicle information source like All Data DIY, and a manual boost pressure gauge.
Begin by thoroughly inspecting all wiring, turbocharger supply hoses, and vacuum hoses related to the turbocharger and boost control system.
Next, connect the scanner to the vehicle diagnostic connector and retrieve all stored trouble codes. Write down the codes and pertinent freeze frame data, as it may be helpful later in the diagnosis. Clear the codes and, if possible, test drive the vehicle to see if the code is reset. If the code immediately resets, perform a manual boost pressure test and compare the actual findings with the manufacturer’s specifications. If the actual boost pressure exceeds the maximum requirements, suspect a problem in the bypass control system or outlet piping system.
Normal boost pressure for modern forced air induction systems is typically between nine and fourteen pounds. If the actual boost pressure is within the manufacturer’s specifications, suspect a defective boost pressure sensor, a faulty PCM, or a PCM programming error. Use the DVOM and your vehicle information source to test the boost pressure sensor and system circuits as needed.
