P0299: Turbocharger/Supercharger Underboost
P0299 is a powertrain diagnostic trouble code in the fuel and air metering — injector circuit group. Our vehicle database stores it against 56 models.
What P0299 actually means
P0299 is one of the most widely logged codes in our database — 56 models record it. It is a powertrain code in the fuel and air metering — injector circuit group, and it is a generic code defined by SAE J2012 and shared by every manufacturer.
The stored definition for P0299 is “Turbocharger/Supercharger Underboost”. The first character of the code identifies the system — Powertrain in this case. The second character tells you who defined the code: this one is a generic code defined by SAE J2012 and shared by every manufacturer. Reading the code that way matters: a generic code tests the same underlying condition on almost every vehicle, so the causes below apply broadly across makes.
Within that system, P0299 sits in the fuel and air metering — injector circuit group. That is the part of the vehicle the control module was watching when it set the code — the electrical side of the injectors — the driver circuit and its wiring rather than the injector itself — and it narrows down enormously where a technician will start looking. Injector-circuit faults are confirmed by measuring coil resistance and watching commanded duty cycle against actual delivery.
What makes P0299 easy to get wrong. Underboost means the turbo is not making the pressure the ECU commanded. The fault can be a leak anywhere between the compressor and the intake — a split intercooler boot is the classic — or a wastegate that is not closing. The code alone cannot separate those, which is why a boost-leak test comes before parts.
How serious is P0299?
We rate P0299 as Moderate — diagnose soon. That rating comes from the severity recorded in our database for this code, not from how alarming the name sounds.
A moderate-severity code usually leaves the vehicle drivable, but the underlying fault tends to worsen and can cascade into a more expensive repair. It is reasonable to drive cautiously to a workshop in the near term, but the code should be diagnosed rather than cleared and forgotten.
Most likely causes of P0299, ranked
Our database records 15 causes for P0299, ranked by how many of the 56 models that log this code report each one. A cause that shows up across many different platforms is a more probable starting point than one tied to a single model.
- Wastegate rattle — the most widely recorded cause, appearing on 40 of the 56 models.
- cracked charge pipe — recorded on 26 of the 56 models logging P0299.
- degraded turbo — recorded on 26 of the 56 models logging P0299.
- cracked intercooler boot — recorded on 14 of the 56 models logging P0299.
- boost leak — recorded on 8 of the 56 models logging P0299.
10 further causes are recorded in the database for P0299; the full list is available in the cross-reference.
Causes are listed as recorded in the database. The same code can have different root causes on different vehicles, so the ranking is a starting order for diagnosis rather than a diagnosis in itself.
How a technician diagnoses P0299
Diagnosis for P0299 follows the same logic as any stored powertrain code: confirm the code is active rather than historic, then work through the ranked causes from cheapest and most likely to most intrusive. In practice that means:
How a technician works P0299 — decision path
Powertrain codes respond to data. Capture the freeze frame, then work through the ranked causes from cheapest and most likely to most intrusive.
- Confirm the code is active and capture freeze-frame dataThe snapshot recorded when the code set holds the engine speed, load, coolant temperature and fuel trims at that moment — often the single most useful piece of evidence for separating one candidate cause from another.
- Compare live data against the freeze frameRe-create the conditions from the snapshot and watch the relevant sensors live. A value that cannot reach the expected range narrows the search immediately.
- Work the ranked causes from cheapest and most likelyThe list on this page is ordered by how many of the recorded vehicles show each cause. Start at the top: an intake leak, a dirty sensor or a worn cap is far more common than a failed assembly.
- Repair the confirmed cause, then re-check the monitorsFix what the evidence actually points at rather than replacing parts speculatively — a misfire or lean code will re-set if the real cause is still present.
- Clear the code and complete a full drive cycleClearing alone proves nothing. The code must stay clear through a drive cycle that reproduces the original conditions, and the readiness monitors must run again.
If a workshop replaces a component for P0299 without showing you the measurement that condemned it, ask for the data. On a fuel and air metering — injector circuit code, the recorded causes are usually testable, so a diagnosis should be demonstrable rather than asserted.
What drives the cost of fixing P0299
We deliberately do not print a single repair price for P0299. Injector work splits cheaply: a connector repair is quick, while a set of injectors is not. The honest answer is that the cost is set by which cause is actually present, and that range is wide — a repair for the first cause listed above and the last can differ by more than an order of magnitude in parts alone: a repaired terminal and a full set of injectors are not the same job. Add regional labour rates and the spread becomes wider still.
The factors that actually move the number, in rough order of impact:
- Connector or injector. The cheapest fix in this group is a repaired pin or terminal, not a part — the circuit is measured before injectors are condemned.
- One injector or the set. Balance and flow testing decides whether a single injector or the whole set is replaced.
- Intake manifold removal. On engines where the injectors sit underneath the manifold, access labour can exceed the parts cost.
- Diagnosis billed separately. Ask whether the diagnostic charge is credited against the repair before authorising work.
The practical approach: get the cause confirmed first, then collect two or three written quotes for that specific repair. To judge whether the repair is worth doing against the value of the vehicle, use our repair-or-replace decision guide.
Vehicles in our database that log P0299
This is one of the most widely logged codes in our database — 56 models record it. The makes appearing most often are Ford (13), Toyota (6), Cadillac (4), Hyundai (4), Kia (4). Each model links to its own guide, where this code appears alongside that vehicle's full fault list and running costs.
Frequently asked questions about P0299
What does the P0299 code mean?
P0299 is a powertrain trouble code meaning "Turbocharger/Supercharger Underboost". It belongs to the fuel and air metering — injector circuit group of the SAE J2012 numbering scheme, and it is a generic code defined by SAE J2012 and shared by every manufacturer. The code is set by the powertrain control module when the monitored system reports a value outside its expected range.
Is it safe to drive with P0299?
Severity for P0299 is rated medium in our database. A moderate-severity code usually leaves the vehicle drivable, but the underlying fault tends to worsen and can cascade into a more expensive repair. It is reasonable to drive cautiously to a workshop in the near term, but the code should be diagnosed rather than cleared and forgotten.
What are the most common causes of P0299?
In our vehicle database, the causes recorded for P0299 are: Wastegate rattle; cracked charge pipe; degraded turbo; cracked intercooler boot; boost leak; Wastegate; boost tube leak; Turbo wastegate / VGT issues; turbo wastegate sticking; VGT actuator; Wastegate regulator; boost leak on diesel; Turbo actuator; VGT turbo issues; Wastegate sticking. They are ranked on the page by how many of the 56 vehicles that log this code list each cause.
How much does it cost to fix P0299?
We do not publish a single figure for P0299 because the real cost depends entirely on which cause is present — a repair for the cheapest cause on the list and the most expensive one differ by an order of magnitude, and labour rates vary by region. The page explains which factors drive the cost and recommends collecting written quotes before authorising work.
Which vehicles commonly report P0299?
Our database stores P0299 against 56 vehicles, most frequently from Ford (13), Toyota (6), Cadillac (4), Hyundai (4), Kia (4). The full list is shown on this page and each model links to its own cost and fault guide.
Related codes and next steps
Codes that share the same system group often appear together, because a single fault can set more than one:
For the full list, see the OBD-II fault code cross-reference. If the repair cost is what you are weighing, model the total with our total cost of ownership calculator before deciding, and check whether an open safety recall covers the fault with the recall lookup.
Sources and scope
Code definitions follow SAE J2012 / ISO 15031-6 naming. The descriptions, listed causes, and severity ratings on this page are the values stored in the VehCalc vehicle database (snapshot 2026-08-20) for the models listed above. Codes and causes vary by model year and engine.
Diagnostic reference only — not repair advice. This page is provided for educational and planning purposes and does not replace an inspection by a qualified technician or the manufacturer's service information. Before repairing a vehicle you depend on, confirm the diagnosis with an ASE-certified mechanic.