P0033 Turbo charger bypass valve control circuit

This code indicates that there is a problem with the turbocharger bypass valve control circuit, which regulates the boost pressure before it enters the engine intake manifold.

If you have a turbocharged or supercharged engine, you may encounter the diagnostic trouble code (DTC) P0033. In this article, we will explain what this code means, what causes it, what symptoms it may produce, and how to troubleshoot it.

What is the P0033 Code?

The P0033 code is a generic OBD-II powertrain code that applies to all makes and models of vehicles (1996-newer) with a turbocharged or supercharged engine. The code definition is:

P0033 Turbocharger / Supercharger Bypass Valve Control Circuit

The powertrain control module (PCM) monitors the turbocharger bypass valve control circuit, which consists of an electronic actuator (or a vacuum control valve) and a sensor. The actuator controls the position of the bypass valve, which opens or closes to divert some or all of the exhaust gas away from the turbine wheel of the turbocharger. This reduces or increases the boost pressure depending on the engine load and speed. The sensor provides feedback to the PCM about the actual position of the bypass valve. 

The PCM sets the P0033 code when it detects an input signal from the turbocharger bypass valve control circuit that is not within the programmed specifications. This could mean that the circuit is open, shorted, or has a high or low voltage. 

What are the Related DTC Codes?

There are some other DTC codes that are related to the P0033 code. They are:

• P0034 Turbocharger / Supercharger Bypass Valve Control Circuit Low
• P0035 Turbocharger / Supercharger Bypass Valve Control Circuit High
• P0036 Turbocharger / Supercharger Bypass Valve Control Circuit Range/Performance
• P0037 Turbocharger / Supercharger Bypass Valve Control Circuit Intermittent

These codes indicate more specific problems with the turbocharger bypass valve control circuit, such as low or high voltage, out of range signal, or intermittent signal.

What are the Causes of the P0033 Code?

There are several possible causes for the P0033 code to set. They are:

• Bad turbocharger bypass valve actuator: The actuator is responsible for moving the bypass valve according to the PCM's commands. If it is faulty, it may not respond properly or at all, causing an incorrect or no signal to be sent to the PCM. 
• Defective turbocharger bypass valve: The bypass valve is a mechanical component that opens or closes to regulate the boost pressure. If it is stuck, damaged, or leaking, it may not operate as intended, causing an incorrect or no signal to be sent to the PCM.
• Disconnected, cracked, or collapsed vacuum line (vacuum actuated bypass valve): Some bypass valves are controlled by vacuum instead of electricity. If the vacuum line that connects the actuator to the vacuum source is disconnected, cracked, or collapsed, it may cause a loss of vacuum pressure, preventing the actuator from moving the bypass valve.
• Faulty boost pressure sensor: The boost pressure sensor measures the amount of boost pressure in the intake manifold and sends a signal to the PCM. If it is faulty, it may send an inaccurate or no signal to the PCM, causing a mismatch with the signal from the bypass valve control circuit.
• Shorted or open wiring in the boost sensor circuit: The wiring that connects the boost sensor to the PCM may be shorted or open due to damage, corrosion, or loose connections. This may cause a loss of communication between the sensor and the PCM, resulting in an incorrect or no signal being sent.
• Loose, corroded, or disconnected electrical connectors in the boost sensor reference circuit: The electrical connectors that link the boost sensor to its power and ground sources may be loose, corroded, or disconnected due to wear and tear, moisture, or dirt. This may cause a loss of voltage or ground in the boost sensor circuit, affecting its performance and signal output.
• Defective PCM or boost controller: The PCM or boost controller is responsible for calculating and commanding the desired position of the bypass valve based on various input data from different sensors. If it is defective, it may send an incorrect or no signal to the bypass valve actuator, causing an error in the bypass valve control circuit. 

What are the Symptoms of the P0033 Code?

The symptoms of the P0033 code may vary depending on the severity and cause of the problem. Some of the common symptoms are:

• Reduced engine performance: If the bypass valve is not working properly, it may affect the boost pressure and the air-fuel ratio in the engine. This may result in reduced power, acceleration, and fuel efficiency.
• Whining or rattling noises from the turbocharger or turbo pipes: If the bypass valve is stuck, damaged, or leaking, it may cause abnormal noises from the turbocharger or the turbo pipes due to excessive or insufficient boost pressure. 
• Excessive smoke from the exhaust: If the bypass valve is not working properly, it may cause too much or too little air to enter the engine, resulting in incomplete combustion and increased emissions. This may produce excessive smoke from the exhaust, especially black smoke.
• Fouled spark plugs: If the bypass valve is not working properly, it may cause too much or too little fuel to enter the engine, resulting in rich or lean conditions. This may cause the spark plugs to foul and misfire.
• Elevated engine and/or transmission temperature: If the bypass valve is not working properly, it may cause too much or too little boost pressure, affecting the engine and transmission cooling systems. This may cause overheating and damage to the engine and transmission components.
• Abnormal hissing noises from the turbocharger wastegate and/or hoses: If the bypass valve is not working properly, it may cause a leak in the wastegate or the hoses that connect it to the bypass valve. This may cause a hissing noise due to escaping air.
• Additional codes may also be stored, including turbocharger boost related codes, engine misfire codes, or knock sensor codes. These codes indicate more specific problems with the turbocharger system, engine performance, or engine detonation. 
• If applicable, the boost pressure gauge may also exhibit abnormal levels of boost pressure. This may indicate that the bypass valve is not regulating the boost pressure correctly.

How to Troubleshoot the P0033 Code?

To troubleshoot the P0033 code, you will need a scan tool, a digital multimeter, a vacuum gauge, and a repair manual for your specific vehicle make and model. The following steps are general guidelines for diagnosing and fixing this code. You should always consult your repair manual for more detailed instructions and specifications.

1. Scan your vehicle for codes. Use a scan tool to retrieve any stored codes and freeze frame data from your vehicle's PCM. Note down any codes and their definitions, as well as any relevant information from the freeze frame data, such as engine speed, load, temperature, etc. Clear the codes and test drive your vehicle to see if they return.
2. Inspect the turbocharger bypass valve and its components. Visually inspect the bypass valve, its actuator (or vacuum control valve), its sensor, and its wiring and connectors for any signs of damage, wear, corrosion, or loose connections. Check for any leaks in the bypass valve or its hoses. Replace any faulty parts as needed.
3. Test the turbocharger bypass valve actuator. Depending on your vehicle's system design, you may have an electrically controlled actuator or a vacuum controlled actuator. To test an electrically controlled actuator, disconnect its electrical connector and use a digital multimeter to check for resistance across its terminals. Compare your reading with your repair manual's specifications. If it is out of range, replace the actuator. To test a vacuum controlled actuator, disconnect its vacuum hose and use a vacuum gauge to apply vacuum to it. Observe if it moves smoothly and holds vacuum. If it does not move or leaks vacuum, replace the actuator.
4. Test the turbocharger bypass valve sensor. Disconnect its electrical connector and use a digital multimeter to check for voltage and ground at its terminals with the key on and engine off (KOEO). Compare your readings with your repair manual's specifications. If they are not within range, check for continuity and resistance in the wiring and connectors of the sensor circuit. Repair any open or shorted wires as needed. If they are within range, reconnect the sensor and backprobe its signal wire with a digital multimeter

Don’t forget to share it