P0299 Code: How To Fix Turbo A Underboost Condition [Repair Vehicle Fault] (2023)

Similar symptoms can point to several possible issues with the car. There comes the OBD-II scanner to help you identify the underlying problem. If you experience acceleration hesitation, illuminated check engine light, or strange noises coming from the engine, you need to diagnose the problem with an OBD-II scanner. If you get a P0299 code, that doesn’t mean much without the explanation of the code.

So, what the P0299 code means? It will notify you about a turbocharger/supercharger “A” under boost condition. A turbocharger uses exhaust gases to turn the turbine. If the gas pressure is too low, then the level of power will drop. That will result in a drop in performance. The “A” in a code means that the vehicle is having more than one turbo or supercharger.

How serious this problem is connected with the symptoms you are getting. If you are having severe drivability and performance issues, you should address them immediately. Even in cases where you are not identifying any problems, you should do a thorough check of the engine. This error code is not a code you want to erase and forget about. Resolve it.

P0299 OBD2 Code: What Does it Mean?

The P0299 code results from low air pressure coming to the turbine of the turbocharger. The problem can be vacuum leaks, EGR issues, a damaged turbo, or a problem with the boost pressure sensor. The result is that the engine will not accelerate as it should. Depending on the vehicle, the ECU may even trigger a limp mode.

The Role of the Turbocharger

The turbocharger is a result of an improvement in naturally aspirated engines. In naturally aspirated engines, the intake air is forced into the intake manifold and the combustion chamber by atmospheric pressure. The turbocharger compresses the air before it gets into the intake manifold and the combustion chamber. That way, more air can enter it. More air means more fuel density, resulting in higher power output.

The P0299 Code: A Technical Breakdown

The turbocharger is made of two main components – the turbine wheel and the turbine housing. The turbocharger is using exhaust gases to make extra power. The turbine housing is guiding the gases to the turbine. The energy in the gases is turning the turbine. Once the cycle is complete, the gases exit the turbine housing through the exhaust outlet area.

If the pressure of the gases is too low, the turbo will not be able to make enough power. The engine control unit (ECU) is monitoring this information through the boost pressure sensor. If the values are too low, the ECU will signal a P0299 code.

Tracing the Causes Behind the P0299 Code

The most common reasons for the P0299 code are:

• Blocked air supply
• Problems with a boost pressure sensor or boost controller
• Vacuum leaks

These problems are grouped into mechanical issues, problems with sensors, and issues with vacuum leaks.

Mechanical Issues

Several mechanical problems can cause a turbocharger to malfunction:

• A blocked or clogged exhaust gas recirculation EGR valve. The usual cause for this is carbon buildup
• A clogged air intake system. It will reduce the effectiveness of the turbocharger
• Blocked catalytic converteror the air filter
• Carbon-induced clogs inside the turbocharger. Carbon buildup can result in failing bearings and turbine overheating
• Leaks causing vacuum actuator failure. The vacuum actuator controls the throttle and the fuel injection
• A defective wastegate valve or solenoid issues. The valve remains closed until the proper booster pressure is achieved. But, in case of a solenoid failure, the valve will stay open. The supercharger consequently cannot create a boost.

Sensor and Electrical Problems

Boost pressure sensor (BPS) monitors the air pressure, and provides this information for the ECU. The ECU then can conduct a correction if needed. With the information about the air pressure, the ECU can determine how much fuel is needed for the combustion process.

A proper air-to-fuel ratio is essential for the overall good work of the engine. If this ratio is bad, that can cause sudden drops in performance, problems with acceleration, and stalling.

In case the boost pressure sensor is worn, old, or damaged, it will not work properly. It may send incorrect information, resulting in performance issues. The problem can be in the sensor itself or boost pressure sensor wiring and connectors.

Besides the faulty boost pressure sensor, a bad boost controller can be the culprit for the P0299 error code. A boost controller regulates how much boost pressure the turbocharger is going to make. In a sort, it is a controlled air leak. It can release any excess boost pressure, preventing engine damage. If it is faulty, it can cause an under-boost problem.

Vacuum Leaks and Their Consequences

An air leak can manifest itself on both the vacuum side and on the system pressure side. That means the leak can be on the intake to the turbo inlet. It can also be anywhere from the turbo outlet to the engine intake manifold.

In both cases, air leaks result in air supply shortages. The major and most common problem is under-boost when the system cannot generate the required air pressure. When the air pressure is low, that will cause problems in the combustion process. The system may try to overcompensate by adding extra fuel.

That will result in a significant drop in performance. The engine will struggle to accelerate, and it will consume more fuel.

Air leaks also cause an increased load on the turbo, provoking extensive damage. An air leak can easily destroy a turbo.

Warning Signs: Symptoms of the P0299 Code

The most obvious symptom of a P0299 code is the check engine light. But that can result in dozens of different problems. The more certain symptoms of a P0299 fault code are:

• Loss of power when accelerating
• Reduced power output
• Increased fuel consumption
• Strange noises coming from the engine bay (whining and hissing)
• Activated limp mode

Engine Performance Issues

When the turbo is not receiving enough air, it cannot perform properly. The air-to-fuel ratio will not be correct, and the combustion process will not be good. In that case, the engine will have lower performance when the turbo needs to activate. Besides that, the engine will struggle with performance constantly.

Unusual Noises and Vibrations

Sometimes, the P0299 error code is followed by strange noises and vibrations. Their cause is usually the vacuum leak.

Warning Lights and Error Messages

The first case, in the majority of cases, is an illuminated check engine light. When the ECU measures or detects any strange value on different sensors, it will trigger it. To determine what is causing the light to turn on, you will need an OBD-II scanner.

How To Fix the P0299 Code: DIY Techniques

Fixing the P0299 is not an easy task, even for a mechanic. You can do basic diagnostics, like checking the OBBD-II codes and visually inspecting the BPS and MAP sensors. Anything more complex should be left to the mechanics.

Check Out Turbo Under Boost Problem Solved, Code P0299:

Diagnostic Tools You Can Use

It is always recommended to check the car for additional OBD-II error codes. If some other code comes together with the P0299, it is better to determine the causes for other error codes first. An example is an error P0106. If you get both the P0299 and P0106, there is a good chance that the problem is in the bad manifold absolute pressure (MAP) sensor.

To check the MAP sensor you will also need a multimeter. For the inspection of the wastegate and wastegate actuator, you will need a manual air pump with a gauge.

Effective Inspection Procedures

If you want to do a checkup, this is the best and simplest instruction. This is a recommended diagnostic procedure that gives the best results. That way, you can first identify all the possible problems. Then, one by one, you can resolve them and reach the proper diagnosis.

1. Run an OBD-II scan. See if there are any other active error codes besides the P0299. Some codes can come together with this code and can point to a certain issue
2. Check the hoses and pipes for leaks. Inspect the intake and turbo hoses and look for a leak between the turbocharger and the manifold. Sometimes it is hard to identify a leak. We recommend using a turbo boost leak tester
3. Investigate the condition of the turbocharger. The first thing to check is the turbo leaking oil. Next, check if the turbine axle is wobbly. Also, look for any cracks in the turbo
4. Check the wastegate and its actuator. For this, you will need a manual air pump that you can fit onto the wastegate. The test is done by supplying the wastegate with the air from the pump. You need to check how much air pressure is needed to open the wastegate. If there is no pressure buildup, or you can see the actuator through the turbo, the wastegate might be stuck open
5. Inspect the MAP pressure sensor. This is done with the multimeter. Check all three wires going into the MAP sensor with a positive probe. The negative probe needs to be grounded. The wires that you are checking are the power, ground, and signal wires. Turn the ignition key on, but do not start the car. Probe the power wire, and you should get a 5V readout. Now inspect the ground wire. The readout should be less than 100 millivolts. If the value is higher, the ground is bad. Check the user’s manual before you check the signal wire. Once you know the regular values, check the wire. If the readouts are off the charts, then the MAP sensor is faulty

Quick Fixes For P0299 Common Issues

Fixing a P0299 code is usually not easy. Depending on the issue, you may need to fix the MAP or BPS, which is doable. You can also try to fix pressure leaks caused by the damage in the intake air system. Sometimes the problem is in the clogged air filter. But, if the problem is more serious, it is advised to contact the mechanic.

Seeking Professional Help for the P0299 Code

If diagnosing these problems is not comfortable with you you should contact a mechanic. Even if you know a thing or two about mechanics, if you hit a wall, leave this to the professional.

When to Contact a Certified Mechanic

If the problem involves replacing the EGR or the turbocharger, it is best to contact the mechanic. He will do a complete troubleshooting of the car, and get to a comprehensive diagnosis. They are experts at their job and can fix even more severe problems that are causing the P0299 code.

Diagnostic Process: What to Expect

1. The technician will hook up the OBD-II scanner to your car. He will scan for all errors and note them through the freeze frame data. Through it, it is possible to see which conditions provoked the error code to appear. After that, he will delete all the codes and go for a test drive to check which errors will reaper and when
2. After the diagnostic, the mechanic will conduct a visual inspection. That includes checking of the turbo/supercharger, the air intake system, and the EGR system. The inspection includes any other components that can be connected to this problem
3. The technician will check the sensor readouts of the boost pressure sensor
4. The mechanic investigates the oil pressure and the air intake systems for leaks or blockages
5. In the end, the mechanic checks the mechanical systems of the turbocharger

Repair Solutions and Costs

The price of repair varies from car to car, but here you can get an approximate cost list:

• Faulty turbo replacement: at least $1,500
• Air intake hose: $100-$300
• Boost sensor: $100-$200
• EGR: $100-$1,000

FAQs: Questions about the P0299 Code

Need More Help with a P0299 Code?

If you tried to diagnose and resolve a P0299 and couldn’t, it is better to contact the mechanic. Some problems are too complex to be resolved without professional equipment. Also, you cannot put a price on a unique mechanic experience. We advise you not to drive the car with this error. Find a good and respected mechanic that can resolve this issue. That way, you can avoid costly damage.