P0299 Ford F150: What Does This Code Mean and How to Fix?

Are the Check Engine or Service Engine Soon warning lights present in your F150's instrument cluster? Does your truck lack the power you were used to and has gone into limp mode, but nothing seems to have gone wrong with its engine?

P0299 code highlights

• Level of urgency:Medium
• Possible culprits:Turbocharger issues, fallen off or cracked pipes, air leak problems
• Price for repair:$150 - $800
• If neglected:Loss of power, harsh work, poor efficiency
• DIY repairs:Impossible
• Can you drive?Carefully

What does limp mode mean?

You might have probably heard before that a vehicle's engine or transmission has gone into limp mode, but what does it mean? This particular feature is a safety measure that is engaged whenever the control units of the aforementioned components detect a fault that could do permanent or severe damage to them.

Things like different options could be deactivated or even the engine's power might be limited to just enough so you can cruise to your home or to the nearest shop. It will usually be very obvious when this function is engaged since the car's behavior will be very different and you might also get an additional warning light telling you so.

What is a diagnostic?

In the last couple of decades, the word diagnostic has been said a whole lot of times in every single shop on this planet.

Why? Simply because it's a fantastic tool that makes troubleshooting way easier than having to do the trial-and-error method. It doesn't matter what warning light you have in your instrument cluster, the diagnostic will tell you something about it. It is also useful for reading live data, such as engine coolant temperature, air intake temperatures, oxygen sensor values, and many others.

The great thing is that there are both universal and dedicated diagnostic tools available now, and some of them for decent prices. The ones dedicated to each manufacturer are usually a lot more expensive, but they also show more information about the vehicles they can be used on. Most of the time, a universal one will do the job just fine.

You may have also heard about terms like OBDII or EOBD and these stand for On-board diagnostics and European on-board diagnostics respectively. They are regulations regarding vehicle diagnostics and have been mandatory since 1996 in the United States and since 2001 (2004 for diesel-powered vehicles) in Europe.

A very important thing to note is that while the diagnostic will help you read error codes, it will not always tell you exactly what is wrong or what component needs to be changed. Certain errors can be caused by multiple issues, so you have to check every single one of them before swapping a good part for another one and still not fixing the issue.

My advice for you would be to start with the cheap and easy stuff and then work your way to the most expensive components.

How to interpret the codes?

Error codes can be a little bit confusing, so I'm going to give you a simple explanation of what they mean. We will use as an example the code that concerns us, P0299. Error codes can begin with one of the four letters: P - Powertrain (engine and transmission included),  B - Body (including airbags and A/C), C - Chassis (ABS included), and U - Network and vehicle integration (wiring bus and everything related to functions managed by onboard computer systems).

The next character is either number 0 (generic code) or number 1 (manufacturer-specific code). Then, we have a number indicating the system that is at fault. There are 8 categories, in our case 2 meaning there's a problem related to the fuel and air metering system.

The last two numbers can range from 0 to 99 and they are more specific to what exactly is wrong in the specified system. In our case, the P0299 error code on a Ford F150 can be translated to Turbocharger/Supercharger Underboost.

What causes the P0299 error on the Ford F150?

To be a little bit more specific, this error code will be present whenever the turbocharger is not able to hold or even produce the desired boost commanded by the PCM (Powertrain Control Module). The issue will be more apparent whenever the engine is under a higher load. Let's see what could be the source of the problem.

• Air leaks - With age and mileage, hoses can get brittle over time, so it's worth visually inspecting them to see if they are cracked or even torn apart. If the hoses themselves seem to be in good shape, you could also check the clamps and make sure they are tight and fit properly. If you have any of these problems, you might probably be able to actually hear the air leak.
• Wastegate stuck open - Make sure that nothing is blocking the actuator and if it isn't the case, check the vacuum lines for leaks.
• Faulty EBOV (Electronic Blow-Off Valve) - This seems to be quite a common problem with these cars, so it's definitely worth checking. There could be a pinched O-ring or even a torn diaphragm. Replacing it usually solves the issue.
• Faulty sensors - MAP (Manifold Absolute Pressure), throttle inlet pressure, and wastegate pressure sensors could also cause this kind of issue. Before checking anything else, make sure that they are plugged in correctly, especially if you have recently had any work done on your car and the mechanic might have forgotten to connect everything back.
• Damaged wiring - This is something that could become a bit of a headache. There are many wires for many electrical components and you should check every single one of them related to the vehicle system you're troubleshooting, in this case, everything related to air metering. Plugs could be damaged because of oil leaking onto them (now you might understand the importance of addressing any oil leak as soon as possible) and wiring could be crumbling because of the heat or even split in certain areas. A good piece of advice that I could give you would be to avoid parking in places where there might be rodents since they absolutely love to chew into insulation and wiring.
• Damaged charge air cooler - Check for any obvious damage caused by any foreign unwanted objects and also for oil leaks. Bad-charge air coolers can also cause all sorts of underboost problems.
• Damaged turbocharger(s) - Unfortunately, tired turbochargers can cause this kind of problem, so it's important to know that if nothing else is faulty, the problem might be with the turbocharger(s). They can be expensive to replace, but a cheaper alternative to buying brand-new ones would be to refurbish the ones on your car since they might be saved.

How to fix the P0299 error on the Ford F150?

Fixing this issue can take some time, so make sure to prepare yourself accordingly. Also, before buying or replacing any component, make sure you check everything that can be fixed easily and without special tools. When dealing with this kind of problem, it is a matter of thoroughly checking every single component in the system until you get to the actually faulty one.

The thing that seems to cause most of the issues is, as mentioned before, the electronic blow-off valve. The part itself, also known as the turbocharger boost pressure relief valve, is relatively cheap and simple to replace. It is held on simply by two 8mm bolts and it's mounted on the side of the charge air cooler.

Access is greatly improved by removing the charge air cooler altogether. Remember to unplug the electrical connector to avoid damaging the plug or the wiring. Another great tool that would really help you when removing and replacing certain components would be a dedicated service manual that shows you (pictures included) exactly what needs to come off, what size bolts, and the very important tightening torques.

Is it safe to drive a car in this state?

Since the car will usually be in limp home mode, which means that the functionality and power will be limited, it is safe to drive your car like this, but it is definitely not recommended because it may affect other components that would otherwise be in perfect working order. The best thing to do would be to drive the car only if absolutely necessary and, preferably, to the nearest shop.

Conclusion

While error codes shown when performing a diagnostic can be very useful when troubleshooting a car that isn't performing how it should, it's very important to keep in mind that no diagnostic will be able to pinpoint your exact issue, since many variables need to be taken into account.

As always, remember to always take your time and do things in the right order to avoid extra costs and doing the same job more times than you need to.