Turbo and forced inductionGeneric OBD-II codeUrgency: Garage soon
Code P0299: turbo underboost (insufficient pressure)
P0299 means: turbocharger or supercharger "A": insufficient boost pressure (underboost).[1][2] The engine control unit has detected that the turbo is not delivering the expected boost pressure: the actual pressure falls below what the engine management requests. That is why, to diagnose it, the requested pressure is compared with the measured pressure using a diagnostic tool.[1][2]
What code P0299 means
The engine control unit has detected that the turbo is not delivering the expected boost pressure: the actual pressure falls below what the engine management requests. That is why, to diagnose it, the requested pressure is compared with the measured pressure using a diagnostic tool.[1][2]
It is a generic OBD-II code (it starts with P0), so it means the same on every make; what changes from one engine to another is the most likely cause.[3]
Original definition (SAE J2012): Turbocharger/Supercharger A Underboost Condition[1][2]
Causes of P0299
From most to least likely, according to the sources.
- 1Air leaks in the boost hoses or the intercooler, from a split hose or a loose clamp: this is the most common cause.[1][2]
- 2Faulty wastegate or its actuator, or a seized turbo, which do not regulate the pressure properly.[1][2]
- 3Worn or faulty turbo.[1][2]
- 4Blocked intercooler or intake.[2]
- 5Faulty boost pressure sensor or problems with its wiring.[1][2]
- 6A fault in the exhaust gas recirculation (EGR) system.[1]
Symptoms
- Engine warning light on in the dashboard.[1]Engine warning light: faults that cause it
- Noticeable loss of power, especially when accelerating.[1][2]Less power: faults that cause it
- The engine may go into limp mode (degraded mode), with limited power.[2]Limp mode: faults that cause it
- Whistling or hissing in the engine bay, typical of a pressurised air leak.[2]Turbo whistle: faults that cause it
- Black smoke from the exhaust when accelerating under load.[2]Black smoke: faults that cause it
- Increased fuel consumption.[1]Uses more fuel: faults that cause it
How to diagnose P0299
In order: from the most likely and cheapest to check to the most expensive.
- 1First check the boost hoses and the intercooler: cracks, oil at the joints and loose clamps. This is the most common cause and the cheapest to repair.[1][2]
- 2With a diagnostic tool, compare the boost pressure requested by the control unit with the pressure measured by the sensor while you accelerate.[2]
- 3Check that the wastegate actuator (or variable geometry actuator) moves and that its rod travels the full stroke, and check the solenoid valve that controls it.[1][2]
- 4Check the boost pressure sensor, its connector and wiring, and the EGR valve.[1][2]
- 5Only when everything above is fine, check the turbo: replacing it without first ruling out a leak or a sensor is an expensive mistake.[1][2]
Can I keep driving with P0299?
Garage soon
You can normally get to the garage by driving gently, often in degraded mode, but you should not carry on using the car as normal: the fault can end up causing more serious engine damage.[1][2]
Documented faults related to P0299
Known faults of specific engines and cars, with their repair cost, the affected years and their sources.
Turbo: the most serious faults by engine and car
- High severityVery frequentFrequency: Very frequent1.6 HDiTurbo failure through lack of lubrication (carbon deposits and union filter)On the 16-valve 1.6 HDi/TDCi engines (2004-2011) the turbo can seize because carbon deposits from the oil clog the mesh filter in the union that feeds it. It is a serious, repeat fault: if only the turbo is replaced without cleaning the circuit, it fails again.Repair (garage): €700–€1,050
- High severityVery frequentFrequency: Very frequent2.0 Ingenium diéselTurbocharger failureYes: according to several sources, the turbo is the component that causes the most faults on the 2.0 Ingenium diesel. It fails across a very wide mileage range (from around 35,000 to over 140,000 km) and, if it breaks up inside, it can send oil or metal into the engine and destroy it.Repair (garage): €2,600–€3,000Appears at around 35,000 km
- High severityCommonFrequency: CommonBMW N47Turbo and wastegate valve failureThe N47's turbo does not usually fail from general wear, but because of failure of the wastegate valve, which regulates boost and can seize or lose adjustment, sending fuel consumption soaring; oil leaks from the turbo itself are also common.Repair (garage): €900–€1,800
- High severityCommonFrequency: CommonOM651Variable-geometry turbo failure and its pneumatic actuatorThe OM651's variable-geometry turbo tends to fail at the pneumatic actuator (cracks, loss of calibration) before the turbo itself. Symptoms range from a gradual loss of power to permanent limp mode, with whistling or smoke if the problem progresses.Repair (garage): €500–€3,000
EGR valve: the most serious faults by engine and car
- Critical severityVery frequentFrequency: Very frequentBMW B47EGR cooler leaks with risk of engine fireYes: the EGR valve cooler can suffer internal coolant leaks which, mixed with soot and oil, can reach combustion temperatures; BMW has launched several technical campaigns since 2018 to inspect and replace it because of the risk of engine fire.Repair (garage): €500–€1,500
- Critical severityVery frequentFrequency: Very frequentBMW N57EGR cooler leaks with risk of engine fireYes: like the N47 and B47, the N57 is covered by BMW's service campaign for EGR cooler leaks, which can mix coolant with soot and oil to combustion temperatures. BMW checks free of charge the 6-cylinder engines built between July 2012 and June 2015 because of the fire risk.
- High severityVery frequentFrequency: Very frequentOM651EGR and particulate filter clogging, and emissions software updatesThe particulate filter and EGR clog up with short journeys, as on any diesel with these systems. In addition, Germany's KBA required software updates on several models with this engine between 2018 and 2021 because of a function that reduced EGR outside a temperature range.Repair (garage): €800–€2,500
- Medium severityVery frequentFrequency: Very frequentOM642Emissions defeat device (AdBlue/EGR) and software update campaignGermany's KBA found indications of emissions manipulation in cars with the OM642 engine (alongside the OM651): AdBlue dosing and the EGR changed between the test bench and the road. Mercedes-Benz denied it, but in 2018 it recalled hundreds of thousands of diesels in Europe.
Frequently asked questions
Can I drive with code P0299?
Only as far as needed to reach a garage, and gently. The car usually limits power, and carrying on driving as normal can make the fault worse and damage the engine.[1][2]
Does code P0299 mean the turbo is broken?
Not necessarily. The most common cause is a leak in the boost hoses or the intercooler; it can also be the wastegate or its actuator, a pressure sensor or an EGR problem. The turbo is just one of the possible causes.[1][2]
How is P0299 diagnosed?
Starting with the simplest things: inspecting hoses, clamps and the intercooler; then comparing requested and actual pressure with a diagnostic tool, and checking the actuator, the pressure sensor and the EGR before touching the turbo.[1][2]
Does P0299 mean the same on every make?
Yes. Codes starting with P0 are generic OBD-II codes and have the same definition for all manufacturers.[3]
Will I pass the MOT with code P0299?
If the code has switched on the engine warning light, no: with that light on, the inspection records a serious defect, and on Euro 5 and Euro 6 cars the ITV (Spain's roadworthiness inspection, similar to the MOT) also reads the OBD diagnostic system. Repair the fault before you go; clearing the code just before the inspection does not help either, because it counts as a serious defect.[4]
Not sure what is wrong with your car? Describe what you notice in the symptom diagnosis or see all fault codes.
Sources
Every fact on this page links to its source. If you find an error, let us know.
- 1.Qué significa el código P0299Autodoc Club · Technical documentation · consulted 2 October 2026 · in Spanish
- 2.P0299: Turbocharger/Supercharger A Underboost ConditionCarista · Technical documentation · consulted 2 October 2026
- 3.On-board diagnosticsWikipedia · Other source · consulted 2 October 2026
- 4.Desmontando mitos: ¿puede pasar mi coche la ITV con el testigo de «avería motor» encendido?Diariomotor · Motoring press · published 8 March 2021 · consulted 2 October 2026 · in Spanish