Technical Description of OBD-II Trouble Code
The performance of the Turbo Charger Bypass Valve Control Circuit is outside the acceptable range.
What does that mean?
This diagnostic trouble code (DTC) is a generic OBD-II powertrain code. It is considered generic because it applies to all makes and models of vehicles (1996-newer), although specific repair steps may vary depending on the make and model.
Owners of these brands, including but not limited to VW, Dodge, Saab, Pontiac, Ford, GM, etc., may experience this issue.
A code P0039 Turbo/Super Charger Bypass Valve Control Circuit Range/Performance is stored in turbocharged and supercharged vehicles when the powertrain control module (PCM) has detected a malfunction in the turbocharger or supercharger boost pressure bypass valve control circuit. A service engine soon lamp may also be illuminated. If this code is exhibited in a vehicle that is not turbocharged or supercharged, suspect a PCM programming error.
The boost pressure bypass valve is an electronically controlled valve that is designed to relieve turbo/supercharger boost pressure before it exceeds the manufacturer’s specified limit (usually between nine and fourteen pounds). This is necessary in order to prevent potentially harmful boost pressure levels that could damage the engine in the event of a turbo/supercharger malfunction. The powertrain control module (PCM) or a separate boost pressure control module controls the boost pressure bypass valve. In most cases, the boost controller is integrated into the PCM. The boost controller collects input signals from various engine sensors and uses them to calculate the optimal amount of turbo/supercharger boost pressure. The boost pressure bypass valve is then activated using an electronic solenoid, electric motor, or vacuum control valve to achieve the desired boost pressure. If the boost pressure sensor delivers an input signal to the PCM indicating an inability to successfully control boost pressure, this code will be stored. Additionally, if the PCM detects an input voltage signal that is not within programmed limits for a specified amount of time and under certain circumstances, a P0039 Turbo/Supercharger Bypass Valve Control Circuit Range/Performance code may be stored.
Turbo/supercharger bypass control valve operation is typically accomplished using a solenoid or a small electric motor. Vacuum operated valves are used on some models, but this design is less common. The PCM supplies a direct voltage signal to activate electronically controlled valves, while vacuum actuated valves are controlled using a vacuum control (or vacuum service) solenoid. The vacuum service solenoid is usually supplied with constant voltage, and the PCM outputs a ground signal when the valve needs to be opened to relieve boost pressure. The valve automatically closes when the ground signal is stopped by the PCM. The vacuum actuated bypass valve is controlled using a voltage signal from the PCM applied to a vacuum service solenoid. Opening and closing the solenoid allows engine vacuum to reach the valve as required to actuate opening. Consult the manufacturer’s service manual (or equivalent) for turbo/supercharger bypass control system specifications before beginning a diagnosis.
Code Severity & Symptoms
The conditions that cause this code to be stored can lead to major engine damage from excessive turbocharger boost pressure. Therefore, this code should be addressed urgently.
Symptoms of a P0039 engine code may include:
Causes
Potential causes for this code include:
Diagnostic and Repair Procedures
A good starting point is always to check for technical service bulletins (TSB) for your particular vehicle. Your issue may be a known issue with a known fix put out by the manufacturer and can save you time and money during diagnosis.
When diagnosing a P0039 turbo/supercharger bypass valve control circuit range/performance code, it is recommended to begin with an inspection of all wiring and vacuum hoses related to the turbo/supercharger and boost control system. This should also include an inspection of the battery, battery cables, and battery cable ends.
Proceed by retrieving and making note of all stored trouble codes and freeze-frame data (if available). Clear all stored diagnostic trouble codes from the system using a code reader or scanner. If the code fails to reset, it may indicate an intermittent issue, which can be more difficult to diagnose. Some OBD-II systems will put the boost pressure bypass valve in the wide-open position when this type of code is stored. By clearing the stored codes, the boost pressure bypass valve system can return to a normal mode before continuing testing.
