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There's nothing like hearing a turbo spool up on a wide-open highway. Once you press that pedal down you'll experience a boost of power you can't find in naturally aspirated engines. Even some more economical vehicles have opted for turbo use to save on fuel and squeeze more power out of a small engine.
While turbos are effective components, they don't always work properly. If you notice a loss of power from your turbo accompanied by a check engine light, there's a good chance you're dealing with engine code P0299.
Read on to learn about what this code is, how to diagnose it, and what you can do to get back on the road.
What Is the P0299 Code And the Symptoms?
The P0299 engine code appears when your car's ECU recognizes a low output for your turbo, especially if the output is excessively low. P0299 codes can only be read if you have a check engine light and an OBD-II scanner you can plug into your vehicle's diagnostic link terminal.
Breaking down the code further, it’s for your vehicle's air and fuel metering with the injector circuit. This code will only appear in vehicles that have a turbocharger. Vehicles use turbochargers to get more power out of a smaller engine without adding more fuel by increasing the air volume fed into the engine.
Recycled exhaust gases spin the turbo turbine (hence the spooling sound) to increase intake pressure and send more air through the cylinders for combustion. This is also why there is a "Lag" when you floor the car – the turbo needs a second to spool up.
The most common symptom of code P0299 is the Check Engine Light turning on. Aside from the light, you may hear strange noises coming from your vehicle's turbo when you're driving and reduced engine power. In fact, some vehicles will enter limp mode with this engine code.
What Is Limp Mode?
Limp mode is activated when your vehicle's ECU notices a problem with your engine. It activates limp mode to protect your engine from possible damage and it imposes limits on what you can do behind the wheel. For example, a P0299 Chevy Cruze code will result in the car being locked at low RPMs.
You'll know your vehicle is in limp mode when you notice the following problems:
- The air conditioner and heating may stop working
- Dashboard lights will flash or turn on
- Your engine won't go above 2,000 to 3,000 RPMs
- Automatic cars will lock you into a lower gear
- The car might shake
- Poor performance
- Can't go above 45 miles per hour
Depending on your make and model, these are only some of the symptoms of limp mode.
How Serious Is the P0299 Code And What Are the Causes?
The P0299 engine code is serious. It will cause your engine to perform poorly and most vehicles will enter limp mode to save power and avoid damaging other internal engine components. While you can avoid replacing faulty components if your vehicle is not in limp mode, failing to address this code can result in extensive damage and costly repairs.
What causes a P0299 code?
P0299 engine codes are caused by a few problems. The most obvious cause of a P0299 code is a broken turbo. When the turbocharger breaks, it will result in this code and potentially cause other problems. It could be any issue in the turbo that reduces its ability to produce boost.
Another cause of the P0299 code is low oil pressure or bad oil. If your vehicle doesn't have enough oil to lubricate the turbo turbine it will sustain damage with each revolution until it fails.
Lastly, you may have issues with airflow sensors or the Exhaust Gas Recirculation (EGR) system.
Can I Still Drive with a P0299 Code On My Car?
Is it safe to drive with a P0299 code? No, you can't still drive with a P0299 code. In fact, most vehicles will enter limp mode when this code is activated. Limp mode results in less engine power, a lower top speed, and several other power-saving measures that make it impossible to drive far.
You should only ever drive in limp mode to reach your nearest mechanic or garage. We would recommend towing your vehicle to a shop or home instead of driving it there with the P0299 code.
Keep in mind that not every vehicle will enter limp mode, so you might be able to drive normally. While this is possible, that doesn't mean you should. Doing so will result in extensive mechanical failure throughout the exhaust system, turbocharger, and cylinder heads. It will also mess up timing for combustion and may result in misfires because the turbo isn't generating enough pressure through the intake system.
How Can I Diagnose a P0299 Code?
Diagnosing a P0299 code can only be done with an OBD-II scanner. When using an OBD-II scanner to diagnose this code you'll want to check the freeze-frame data to see when the code first appeared. Once you know when the code appeared you can try to recreate it to see if you're dealing with a faulty sensor or broken components.
To determine if the sensors are faulty, reset the code and take the vehicle for a test drive. If you notice the code appearing again, something is likely not working properly. Then, plug the OBD-II scanner again and read the code. Check the freeze-frame data one more time to see if it's the same issue.
After you know the problem, you can start to inspect the turbocharger and its surrounding systems by checking for boost pressure readings, oil pressure issues, and restrictions in the intake system, and examining EGR components. From here, you can locate and pinpoint the problem's origin.
Next, it's time to inspect and repair the turbo system.
How Difficult Is It to Inspect a P0299 Code?
Diagnosing a P0299 engine code is only the first part of addressing the problem. Once you know where to start you can begin replacing the damaged components. That said, it's challenging to inspect a P0299 code if you've never worked on a car. In fact, it's a challenge code to fix for automotive hobbyists.
What makes the P0299 system difficult to inspect is its location in the engine bay and the systems it's connected to. You'll have to remove the old turbo, seal leaks in the intake system, and replace EGR components to address the problem.
Looking for tools or parts to fix your turbo underboost condition? We can help. JEGS has knowledgeable product experts and a wide range of parts to get you back on the road again, producing all the power you want.
6 responses to “P0299 Code Causes & Fixes – Turbo Underboost Condition”
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to whom it may concern, we had a P0299 code on our 2012 Audi 2.0T Avant. the mechanic said it could be any reasons mentioned in your publication. However, the code was cleared but the check engine light can back on back soon thereafter only to go out again for ca. 1,000+ miles. We neither noticed any difference in drivability, e.g., limp mode, nor did the car make any mechanical noises whatsoever. Now the check engine turned on again. It is hard to fathom that a broken turbo or mechanical wastegate are at fault. Anything we should check out first. The vehicle has 150,000 miles on the odometer and we are a bit reluctant to replace the expensive turbocharger as a first measure without knowing that it is the turbo charger or a mechanical component thereof. Any thoughts?
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Bernd, It’s understandable to be cautious about replacing expensive components like the turbocharger without a clear diagnosis, especially when dealing with a P0299 code. Here’s a guide on what you can check first and potential steps to take:
1. Understanding the P0299 Code:
The P0299 code indicates a turbocharger underboost condition, meaning the engine control module (ECM) has detected that the turbocharger isn’t producing enough boost pressure. This can stem from various issues, and the intermittent nature of your check engine light adds complexity.
2. Potential Causes to Investigate:
Given your description and the absence of drivability issues, consider the following areas before assuming a turbocharger failure:
Vacuum Leaks:
Check for any vacuum leaks in the intake system, which can affect boost pressure. Inspect hoses, connections, and gaskets for wear or damage.
Boost Pressure Sensor:
A faulty boost pressure sensor might lead to incorrect readings, triggering the P0299 code. Testing or replacing this sensor could be a simple fix.
Turbocharger Wastegate:
Since you mentioned not hearing any mechanical noises, the wastegate might be stuck or not functioning properly. Inspecting the wastegate actuator and its connections is crucial.
Intercooler and Piping:
Examine the intercooler and associated piping for leaks or blockages that could hinder boost pressure.
Exhaust Restrictions:
A clogged catalytic converter or exhaust system can impact turbo performance. If there’s a restriction in the exhaust flow, it may lead to underboost conditions.
3. Diagnostics:
Scan Tool:
If you have access to a diagnostic scan tool, monitor the boost pressure readings while driving to see if they correlate with the check engine light.
Pressure Test:
Performing a boost pressure test can help identify leaks in the intake system, ensuring the turbocharger is functioning as expected.
4. Turbocharger Condition:
If after checking the above components you still suspect the turbocharger, consider having it inspected by a professional. Look for signs of oil leaks, excessive shaft play, or other mechanical issues.
5. Consider Previous Repairs:
Review any previous repairs or modifications made to the vehicle. Sometimes, changes in the engine management system or aftermarket parts can contribute to these codes.Given your situation, it’s wise to investigate the simpler and less costly components first. If you find no issues in these areas and the P0299 code persists, a professional inspection of the turbocharger itself may be warranted. Documenting any patterns related to the check engine light’s illumination can also assist your mechanic in diagnosing the issue accurately. Remember, addressing the root cause now can save you from costly repairs later on.
If you need additional help, we are open 7 am-Midnight EST Monday through Friday and 8:00 am-11:00 pm on Saturday and Sunday. Call us at 1-800-345-4545.-
Tenho um HB20 com esse código. Contudo o carro não apresenta perda de potência. Nem problema no ar-condicionado e nem entrou no modo segurança. Pois o carro chega a a mais de 90 km sem problema nenhum. O que pode ser?
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Felipe, code P0299 means the system has detected lower turbo boost pressure than expected. Even if your HB20 is running normally without noticeable power loss or going into limp mode, the code could be caused by an intermittent issue. Possible causes include a leak in the turbo or intercooler hoses and connections, an inaccurate boost pressure sensor, a wastegate or actuator problem, or another component in the boost control system. The fact that the car can reach speeds above 90 km/h without a problem does not necessarily rule these out, since the fault may only occur under certain engine loads or RPM conditions. I would first check for any other stored trouble codes and inspect the hoses, connections, and sensors before replacing any parts. Using a scan tool to compare commanded boost pressure with actual boost pressure during a road test can also help pinpoint the cause.
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In my 2011 Mitsubishi triton mn turbo diesel, when the turbo is under load it starts squelling bad,I’ve replaced the turbo but still did the same thing, what would this be
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Hello Rodney,
The squealing noise in your 2011 Mitsubishi Triton MN turbo diesel, even after replacing the turbo, could be caused by several other factors:
1. **Boost or Vacuum Leaks**: Check all the hoses, intercooler pipes, and connections for any cracks, loose clamps, or leaks. A leak in the intake system can cause a squealing noise as air escapes or enters under high pressure.
2. **Exhaust Leak**: A leak in the exhaust manifold, turbo gasket, or exhaust downpipe can cause a high-pitched squeal, especially under load when exhaust gases are at their highest pressure. Inspect the exhaust system for any cracks, missing bolts, or blown gaskets.
3. **Serpentine Belt or Accessory Drive Components**: A worn or loose serpentine belt, or faulty components like the belt tensioner, alternator, or pulleys, can produce a squealing sound. Under load, the belt can slip or one of these components can struggle, causing the noise.
4. **EGR (Exhaust Gas Recirculation) Valve**: If the EGR valve is sticking or not sealing properly, it might cause a whistle or squeal as exhaust gases leak through. Cleaning or replacing the EGR valve may solve the problem.
5. **Turbo Mounting or Wastegate Issues**: If the turbocharger wasn’t mounted correctly, or if there’s an issue with the wastegate (like a stuck or improperly adjusted wastegate actuator), it could cause the noise under load.
6. **Intake Manifold or Throttle Body**: Inspect the intake manifold and throttle body for any leaks or damage. A gasket failure or cracks in these components can cause a whistling or squealing noise.
It would be best to start by checking these potential causes step-by-step to pinpoint the exact source of the squealing noise. If all of those check out good, a certified mechanic or dealer would have to investigate to find out exactly why it’s making that noise.Hopefully this helps.
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