With the desire to have vehicles pollute less and consume fewer MPGs, but still perform just as well as they did in the good old days, we’re left with resorting to using mechanical trickery and bending the laws of physics to our will. Forced induction is the foremost solution to have come out of that. It’s a neat way to downsize our engines without compromising speed… Until a P0299 code shows up.
It’s a fact that continually adding extra pieces to a machine, thus making it more complicated, would surely add possible points of failure that you’ll have to deal with in time. This includes turbochargers and superchargers, being bolted onto your car to add that bit more gusto to the engine. Yet, for all their many benefits, turbos and superchargers are prone to failure and other issues down the line.
This includes seeing a P0299 code. Whenever you’re seeing this error code, it’s a tell-tale sign that your turbo- or supercharger isn’t creating enough boost when prompted. That boost, of course, is a key component of forced induction systems. It helps to intensely pressurize the air, before jamming it down into the engine to high-intensity explosions. That is unless a P0299 code appears.
What Is Forced Induction, Anyway?
As we take a closer look at a P0299 code, we might as well try to dissect what the component(s) in question do. So, what is this ‘forced induction’ thing, and how does it work? Earlier on, we spoke of its benefits in regards to maximizing performance, even in smaller (hence, fuel-efficient and not-as-polluting) engines. While that remains to be true, forced induction was initially created for speed.
Traditionally, cars were ‘naturally-aspirated’. That is to say, the flow of air rushing into the engine for combustion to take place was ‘natural’ or organic in its volume and pressure. As time passes, some wondered about what would happen if you were to pressurize and force-feed air into the engine. This is where the concept of forced induction is born; added air equates to more performance.
Forced induction sees intaking air being highly compressed and pressurized before feeding it into the combustion chamber. Combined with that, forced induction will also force your engine to cram extra fuel into the mix (to create a meatier air-to-fuel ratio for combustion). More air and more fuel lead to ever-powerful explosions inside the engine, which forces the crankshaft to rotate faster.
Subsequently, simply put, cranking additional chutzpah out of your engine. As far as horsepower and torque are concerned, forced induction (albeit it has its own quirks) is far ahead of natural aspiration. Forced induction is popularly applied in two forms, either using a ‘turbocharger’ or a ‘supercharger’. While they both adopt forced induction, the way they compress and pressurize intaking air differs.
Turbocharging Vs. Supercharging
When it comes to force-feeding the engine with additional intaking air under high pressure, you can’t go wrong with either a turbocharger or a supercharger. It’s been the default choice. However, what are the differences in functionality and performance between them? Well, here’s a quick rundown of how they function:
- Turbocharger – As your engine completes one combustion cycle, it exhausts toxic fumes out through the tailpipes. Before it gets there, with turbocharged engines, the exhaust fumes will first flow into the turbo(s). This rush of surging, hot air will induce the turbocharger to spin a turbine. This then powers a compressor (aka the impeller) to compress fresh air for the following combustion cycle.
- Supercharger – Similarly, a supercharger functions to pressurize, compress, and force-feed intaking air into the engine. Whereas turbos spool up with pressure from the exhaust gases, superchargers instead use a part of your engine’s power. Either using an electric motor or a belt that connects and runs off the crankshaft, a supercharger relies on mechanically-driven energy to get it going.
In either case, the end goal of a turbocharger or a supercharger is one and the same. Choosing one or the other is a matter of what you get out of it. Turbochargers require time to spool up, causing a momentary lag to appear before you feel that power coming in. Superchargers, on the other hand, don’t have that “turbo lag”. Hence, providing an immediate response, but it’s not as fuel-efficient as turbos.
What Is Boost, And Why Does It Matter?
Another crucial point in understanding a P0299 code is knowing what turbo and supercharger boost mean, and why it matters. The term ‘boost’ is used to signify how much pressure a forced induction system (either turbo or supercharger) creates. Boost is measured in pounds-per-square-inch, or ‘psi’. In most newer cars, basic turbochargers have around 6psi to 8psi in boost, which seems quite tiny.
Nevertheless, that small amount is enough to force the (turbocharged) engine to intake upwards of 50% more air compared to a naturally-aspirated setup. It’s for that reason why simple and cheap 4-cylinder motors these days could easily beat out an older (and non-turbo) V6 or V8 for sheer power. Imagine what you could do then, by cranking up that boost pressure to at least double that.
In some cases, turning it up to 14psi or 16psi is sufficient to double the horsepower output of most engines. To prove just how insane it gets, we could take a look at the Lancia Delta S4, an old rally car from the Group B days. While it only had a 1.8-liter 4-cylinder engine, it can easily crank out 1,000hp. This is thanks to its use of both a turbo and supercharger, for a combined 73.5psi of boost pressure.
Naturally, there are limitations to how much boost you can have. Forced induction introduces a lot of extra heat into the engine. Furthermore, and since turbos and superchargers cycle the engine at high RPMs, the engine couldn’t easily cool down. Thankfully, your car’s ECU (engine control unit) manages the boost pressure to prevent it from causing knocking or pre-detonation caused by that extra heat.
What Does A P0299 Error Code Mean?
With all that in mind, we’re now well-equipped to explore further as to what a P0299 code means if it shows up in your car. Typically, diagnostics trouble codes like P0299 will feature an accompanying error message to briefly summarise an issue. With a P0299 code, it’ll show something along the lines of, “Turbocharger/Supercharger A Underboost Condition”. So, what does this denote?
Well, it’s a simple way of saying that your turbo or supercharger isn’t working properly. In particular, its inability to create a sufficient boost pressure when prompted by the ECU. In practice, your turbo and supercharger work through signals and input sent by the ECU. The latter is responsible for how much boost pressure the forced induction system needs to produce, and they’ll duly oblige.
The ECU will up or lower the boost pressure on the fly, depending on various conditions such as the rate of airflow, engine temperature, fuel injection status, and more. If the turbo or supercharger isn’t able to supply the engine with a boost pressure that the ECU specifically requested (given a margin of error), then a P0299 code will appear. This is a warning sign for you that something’s wrong.
A myriad of sensors will carefully monitor and report back the boost pressure to the ECU. They’ll be alerted if that boost pressure is higher or lower than usual. In this case, “underboost” means that it’s not enough. Specifically, a P0299 code relates to the turbocharger or supercharger in your engine’s ‘A’ bank. In other words, only one of the turbo or superchargers (assuming there are two) is affected.
What Causes A P0299 Code To Appear?
Unfortunately, the reasons why a P0299 code appears are much muddier than it seems. There are a lot of root causes of why your turbocharger or supercharger isn’t able to produce enough boost. It could make diagnosis and troubleshooting (more on that later) significantly harder than most other engine issues. That said, we can narrow down the plausible causes of turbo or supercharger problems to:
- Bad mass airflow (MAF) and/or manifold absolute pressure (MAP) sensors (as well as the BARO/BAP sensors for barometric air pressure), which fail to feed the right pressure and airflow rate data to the ECU.
- Faulty solenoids on the turbocharger or supercharger, as that could cause the two to not actuate or monitor the right amount of boost when required.
- Compromised wiring, such as frayed wires, short or open-circuits, and corroded connectors and pins leading to and from the turbo and supercharger.
- Complete turbocharger or supercharger failure, such as seizing, sticking, binding, and so on, as the entire unit might fail (usually owing to oil starvation or oil contamination).
- Bad boost pressure sensor, which would be unable to accurately report back to the ECU on what the right boost pressure actually is.
- Wastegate (which controls the amount of exhaust fumes entering the turbocharger) might be stuck fully open, as it’ll fail to pressurize the boost properly.
- Restrictions or clogging in the intercoolers (they help to cool down hot air that’s compressed by the turbo before heading into the engine).
- Exhaust leaks, as leaking exhaust fumes won’t be able to flow into the turbochargers to force the turbine and compressor to spin.
- Leakage of air in the induction or intake system, or perhaps caused by a clog in the system due to debris and contamination.
- Faulty exhaust gas recirculation (EGR) system, as it’s unable to adequately pump back exhaust fumes into the intake.
- Low oil or fuel pressure, which might prompt the ECU to cut back on the turbo or supercharger’s boost pressure to protect the engine.
- Glitchy or malfunctioning ECU that’s unable to signal the turbo or supercharger correctly, although this is a rare issue.
What Are The Symptoms Of A P0299 Error Code?
It might prove challenging to pinpoint the exact reasons why your turbo or supercharger isn’t producing enough boost. Although, its symptoms should be clear enough. An underboost in the turbo or supercharger will directly impact your car’s performance. As such, you should head over to a nearby mechanic as soon as you begin to see bad turbo or supercharger symptoms. These can include (but aren’t limited to):
- Check engine light (CEL) appears on the dash. This happens as it’s recording and storing the P0299 code (as well as maybe a few other error codes) in the system for later analysis.
- Poor performance, with slow and hesitating acceleration, compared to before. The lack of power will be equally noticeable at higher or lower speeds (RPM) regardless.
- Lack of boost, which you should be able to view in real-time if your car is fitted with a boost pressure gauge. Note the psi readings, and make comparisons.
- Increased fuel consumption. This is a side effect as you’ll have to stab at the throttle harder every time to compensate for the lack of power.
- Odd and noticeable (usually mechanical-sounding, like whining, hissing, or rattling) noises from the turbocharger or supercharger. You can probably hear it cut in and out intermittently.
- ECU might force your car into its ‘limp home’ mode, to further limit engine speeds and protect it from any possible damage until the underlying can be resolved.
- Possible misfiring in one or more cylinders on occasions due to improper combustion. In addition, you might be able to hear a backfiring and popping sound from the exhaust.
- Accelerated wear and damage to the catalytic converters as well as higher tailpipe emissions than before. Albeit, both aren’t easy to notice right off the bat.
How Can You Diagnose A P0299 Trouble Code?
Since you’ve already figured out that you have a P0299 code, what can you do to fix it? First, we’ll have to conduct a thorough diagnosis and testing. Primarily, to try and figure out precisely what’s caused your turbocharger or supercharger to produce a lackluster boost pressure. But as we noted earlier, there could be an array of possible points of failure, which makes diagnosis tricky.
It could be an electrical issue, sensor-related fault, mechanical woes, and so forth. Therefore, it may be easier to let a professional mechanic handle this. But if you’re keen to get your hands dirty, there are some simple diagnostic techniques that could help us. For the most part, it aids you to isolate the true cause towards a particular component and helps you to plan out what needs repairing.
Step 1: Analyse All The Error Codes
First and foremost, grab your OBDII diagnostics tool. Then, you can rescan the ECU for every single error code, including a P0299 code. In doing so, the ECU itself might help point you in the right direction. After all, it’s able to alert you of everything that’s gone awry. This includes the turbo and supercharger.
A P0299 code tells you that your turbo or supercharger isn’t creating enough boost. Meanwhile, any additional error codes could explain why this is occurring. Of course, we’ll try to focus more on all the turbo and supercharger-related error codes. These include (but aren’t limited to):
- P0033, P0034, P0035, P0039 – Bypass valve control circuitry or wiring issues.
- P0046, P0047, P0048 – Boost control problems for Bank A.
- P0049 – The turbine is overrevving and speeding up too much.
- P0235, P0236, P0237, P0238 – Boost pressure sensor woes for Bank A.
- P0239, P0240, P0241, P0242 – Boost pressure sensor woes for Bank B.
- P0243, P0244, P0245, P0246 – Bad wastegate solenoid for Bank A.
- P0247, P0248, P0249, P0250 – Bad wastegate solenoid for Bank B.
- P1247, P1248 – Low or undetected boost pressure (turbos only).
- P1691, P1692, P1693 – Pressure control solenoid circuit malfunction (turbos only).
- P1694 – Faulty charge relief circuit (turbos only).
Once you’ve determined what error codes are present, you can try to reset them with your OBDII tool in the event that it’s merely a glitch. Then, take your car out for a short test drive. See if the codes or aforementioned symptoms reappear for an under-boosted turbo or supercharger.
Step 2: Perform A Visual And Audible Inspection
Now, we can perform more stimuli-related diagnosis steps. First, we can rely on any peculiar or out-of-the-ordinary sounds that the turbocharger or supercharger is emitting. Press on the throttle pedal and listen closely to the type of sound it makes. That’ll be useful to narrow down what’s caused it:
- Hissing – Pressurised and compressed air is escaping from the intakes or turbo/supercharger. This will point you towards an induction or exhaust leak somewhere in the system.
- Whining – For turbochargers, hearing any whining sounds is indicative of a failing or faulty turbo. It’ll likely require significant repairs or a complete replacement.
- Rattling – That clinking and clanking of loose components rattling around could be a sign that your wastegate has failed. Or, that it might be stuck fully open.
But what if none of these audio cues could help you out? In that case, you’ll have to visually inspect each component for any signs of damage or failure. Seeing how many of these parts could’ve caused an underboost turbo or supercharger, this is a tedious process. In particular focus on inspecting the:
- MAF, MAP, and BAP sensors for visible signs of failure, clogging up, or contamination.
- Wiring and cables to make sure there isn’t any fraying, loose connectors, or corrosion.
- Turbocharger and supercharger unit, to see if it’s spooling up and that it’s sealed shut (to prevent any induction/exhaust leaks).
- Intake manifolds and EGR system, ensuring that there aren’t any vacuum leaks or clogging here, too.
- Intake system, to see if there are any cracked, loose, or disconnected hoses.
- Air filters, and making sure there isn’t any debris clogging it up and restricting airflow.
- Fuel pump, and see if the fuel pressure (as well as fuel injection) is working as it should.
- Other solenoids, valves, sensors, and regulators in and around the turbo/supercharger.
How Can You Solve A P0299 Code Problem?
From here on out, you can now undertake the appropriate measures in fixing a P0299 code. It’ll have to depend on your preliminary diagnosis in understanding what components are at fault. What is at least worth reminding is how important it will be to promptly have your vehicle inspected if a P0299 code does show up. Turbocharger and supercharger-related faults shouldn’t be delayed or put off.
Initially, all you might notice is poor performance and compromised driveability. And true, bad turbo or supercharger operation won’t immediately scrap or blow the engine. But if it’s not fixed in time, it can lead to significant issues down the line. Incorrect boost will cause a drop in power, which would lead the engine to mistime its ignition and combustion. Ignoring this can be consequential.
It’ll heavily accelerate wear and tear in the engine, alongside substantial internal damage that isn’t so easily fixable. At that point, you’ll have to spend thousands for a rebuild of the engine. In contrast, repairing turbo or supercharger-related problems early one is much cheaper (although it’s still rather costly as a whole):
- Turbocharger Or Supercharger Replacement – $1,500++ (superchargers are more expensive, costing at least $2,000+ for a full replacement)
- Air Intake Hoses – $100 to $300+ (the cost is similar for any other vacuum hoses and lines, etc.)
- Boost Pressure Sensor – $100 to $200+ (a similar cost applies for most other sensor-related faults)
- MAF, MAP, Or BARO/BAP Sensor – $100 to $400+ (depends on how accessible they are)
- EGR Valve – $150 to $500+ (depending on your car, it might skyrocket to nearly $1,000)
Final Thoughts On A P0299 Error Code
That then rounds up our look at a P0299 code, and what this issue might entail for your car. In all, we learned that it’s prompted when your ECU detects an underboost with your car’s forced induction. Or in other words, a problem with the turbocharger or supercharger. Alas, the actual underlying cause of a P0299 code can vary wildly. Consequently, this applies to diagnosis and troubleshooting.
It might be a simple electronic or sensor-related fault, which is comparatively simple and cheap to resolve. Or, it might scale up to a complete turbo or supercharger failure. The latter might cost you upwards of $2,000 to replace in its entirety. Nonetheless, that’s still somewhat cheaper. Especially, when compared to an extensive engine rebuild or replacement, should you choose to ignore a P0299 code, instead.
