P0299 Turbocharger or supercharger is producing less boost than the engine computer requested

Turbo/supercharger underboost

P0299 in short

P0299 means the turbocharger or supercharger is making less boost than the engine computer asked for. Common causes are a boost leak in the charge-air pipes, a clogged air intake, a sticking wastegate or boost control valve, or a worn turbo. Expect reduced power; get it checked soon.

A turbocharger uses exhaust flow to spin a compressor that pushes extra air into the engine; a supercharger does the same job driven by the engine. The engine computer decides how much boost it wants and measures what it actually gets.

P0299 sets when actual boost stays below the requested amount under load. On the 2008 Saab 9-3, for example, the computer checks during a hard acceleration in third gear and flags any shortfall. The code says boost is low; it doesn't name a part.

Air escaping from a hose or intercooler, a restricted air filter, a wastegate or control valve that won't hold boost, or a worn turbo all cause it, and so can a boost sensor that reads low. Check the cheap things, such as the filter, hoses and clamps, before condemning the turbo, and make sure its oil supply is healthy before replacing it.

Most likely causes

These are general causes for this code across vehicles. None is specific to one make or model.

  1. Boost leak: split, loose or oily charge-air pipe, intercooler hose or clamp

    Common general cause
    Why it ranks here
    Pressurised air escaping between the turbo and the engine never reaches the cylinders, so boost falls short of what the computer asks for. Intake leaks are among the causes KBB lists, and they are cheap to find, so they are checked early.
    What would change this
    A loose clamp, a split hose, oil weeping at a joint or a leak found by pressure testing confirms it; a sealed intake moves the turbo and its controls up.

  2. Restricted air intake, such as a clogged air filter

    Common general cause
    Why it ranks here
    If the turbo can't draw enough air it can't build full boost. Ram's bulletin for some 6.7L Cummins trucks with P0299 has the technician test air handling and possibly replace the air filter.
    What would change this
    A dirty or collapsed filter or a blocked intake duct confirms it; a clean intake rules it out.

  3. Wastegate or boost control valve stuck, leaking or not responding

    Possible — needs testing
    Why it ranks here
    The computer regulates boost through a control valve that operates the wastegate. Saab's diagnostic tool tests and activates this valve when P0299 is stored.
    What would change this
    A valve that doesn't respond to scan-tool activation, or a wastegate that sticks or doesn't move freely, raises this.

  4. Worn or damaged turbocharger

    Common general cause
    Why it ranks here
    Worn bearings, a damaged wheel or a seized shaft stop the turbo spinning freely. KBB calls a faulty turbo one of the most common causes, and Volkswagen issued a bulletin for some Passats with seized or broken turbo shafts.
    What would change this
    Excess shaft play, wheel damage, rubbing or a whine or grinding noise from the turbo raises this.

  5. Low oil pressure or a poor oil supply to the turbo

    Possible — needs testing
    Why it ranks here
    The turbo's bearings depend on a steady oil supply; KBB notes low oil pressure can starve them and make them fail.
    What would change this
    A low oil level, an oil pressure warning or a restricted turbo oil line raises this.

  6. Faulty boost pressure sensor or wiring

    Possible — needs testing
    Why it ranks here
    If the sensor reads low, the computer thinks boost is short when it isn't. Saab's tool compares charge-air pressure with outside air pressure for this reason.
    What would change this
    With the engine off, a boost reading that disagrees with outside air pressure raises this.

  7. Exhaust gas recirculation (EGR) fault

    Possible — needs testing
    Why it ranks here
    On engines that share exhaust flow between the EGR system and the turbo, an EGR fault can rob the turbo of drive. KBB lists it among the causes.
    What would change this
    EGR codes stored alongside P0299 raise this.

  8. Engine computer software

    Possible — needs testing
    Why it ranks here
    Some makers have released a software update for P0299; GM did for one 2022-2023 Silverado engine. It applies only where a bulletin says so.
    What would change this
    A software update listed for your vehicle and engine raises this.

What to test first

Start at step 1. Each result tells you what it means and where to go next.

  1. Read all codes and freeze-frame data. With the engine off, compare the boost pressure reading with outside air pressure, and check for any software update for your vehicle

    Low riskTool: scan tool with live data

  2. With the engine off and cool, inspect the air filter and intake duct, then the charge-air pipes, intercooler hoses and clamps for splits, looseness and oil

    Low riskTool: visual inspection

  3. Have the charge-air system pressure-tested for leaks

    Best left to a shopTool: boost leak tester (shop)

    Warning:Boost leak testing pressurises the intake with shop air. Use a regulated tester at the pressure your maker specifies, keep clear of hose ends and clamps, and leave it to a shop if you don't have the equipment.

  4. Activate the boost control valve with a scan tool and check that the wastegate moves freely through its travel

    Best left to a shopTool: scan tool with activation (shop)

    Warning:The turbocharger and exhaust get extremely hot. Let the engine cool fully, never run the engine with the intake pipe removed, and keep fingers away from the compressor wheel.

  5. With the engine cold, check the oil level and oil pressure, the turbo's oil supply line, and the compressor wheel for damage and shaft play

    Best left to a shopTool: oil pressure gauge; visual inspection (shop)

    Warning:The turbocharger and exhaust get extremely hot. Let the engine cool fully, never run the engine with the intake pipe removed, and keep fingers away from the compressor wheel.

Symptoms

  • Check engine light with noticeably less power or slow acceleration Gets more serious: stop and have it checked.
  • Limp mode: power limited until the engine is restarted or repaired Gets more serious: stop and have it checked.
  • Whistling, whining or grinding from the turbo area
  • Check engine light flashing, or the engine shakes and stumbles under load Gets more serious: stop and have it checked.

Compare with: Check engine light with loss of power

How to fix

  1. With the engine off and cool, check the air filter and replace it if it is clogged.

  2. Look along the pipes between the turbo, intercooler and engine for loose clamps, split hoses and oily residue at the joints, and check the engine oil level.

On your vehicle

Ram

  • 2019–2024 · 2500 · 6.7L Cummins

    Supported by vehicle data

    On 2019-2024 Ram 2500/3500 with the 6.7L Cummins, P0299 with low power or lag calls for an air handling test and possibly a new air filter.

  • 09-003-26Status unverified

    Cummins 6.7L air filter replacement for P0299

    2019–20242500, 3500 · 6.7L Cummins · issued · NHTSA 11029754

    For P0299 with low power, acceleration or lag on 6.7L Cummins trucks, the technician runs an air handling performance test and may replace the air filter.

    We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

Chevrolet

  • 2022–2023 · Silverado 1500

    Supported by vehicle data

    On 2022-2023 Silverado 1500 with the L3B engine, GM issued a service calibration for P0299.

  • 23-NA-045Status unverified

    Engine RPO L3B P0299 service calibration

    2022–2023silverado-1500 · issued · NHTSA 10235624

    GM repair information providing a service calibration for P0299 on the L3B engine.

    We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

Volkswagen

  • 2012–2014 · Passat

    Supported by vehicle data

    On 2012-2014 Passats, VW updated the turbocharger oil supply line for a turbo with a broken or seized shaft and an engine lacking performance.

  • V211601_2036110Status unverified

    Turbocharger oil supply line update

    2012–2014passat · issued · NHTSA 10089101

    For an engine lacking performance with a broken or seized turbocharger shaft, the bulletin updates the turbocharger oil supply line part.

    We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

  • P0106Manifold pressure (MAP) sensor reading doesn't match what the engine computer expects

    Same system Possible — needs testing

    On turbocharged engines the computer judges boost with manifold pressure readings. On the 2008 Saab 9-3, P0106 blocks and resets boost adaptation, so fix a manifold pressure code before chasing low boost.

All Turbocharging, fuel pressure and EGR codes

P0299 questions

Can I drive with P0299?

Usually for a short distance, though power may be limited. Get it diagnosed soon: a failing turbo can damage the engine. If you hear new noises from the turbo, get it looked at promptly, and if the check engine light flashes, stop driving.

Does P0299 mean my turbo is bad?

Not necessarily. Boost leaks, a clogged air filter, a sticking wastegate or control valve and a faulty boost sensor all set the same code. Rule those out before replacing the turbocharger.

Why do turbos fail?

Oil starvation is one cause: the turbo's bearings depend on a steady oil supply, and low oil pressure can wear them out. That is why the oil supply should be checked before fitting a new turbo.

Is there a software fix for P0299?

For some vehicles, yes. GM, for example, issued a service calibration for P0299 on one Silverado engine. Ask a dealer to check for updates for your exact vehicle before replacing parts.

Sources and review

  1. p0299 Code - Turbo Underboost Condition — Kelley Blue Book (KBB Service Advisor)
  2. FCA US (Stellantis) bulletin 09-003-26: Cummins 6.7L air filter replacement for P0299 — FCA US (Stellantis) (filed with NHTSA) ,
  3. Saab 9-3 (2008) WIS DTC P0299 00 (ME9): Turbocharger underboost detected — Saab Automobile (Saab WIS service information, hosted by Saab Club of North America)
  4. Final Regulation Order: 13 CCR §1968.2, Malfunction and Diagnostic System Requirements (OBD II) for 2004 and later passenger cars, light-duty trucks and medium-duty vehicles — California Air Resources Board
  5. 2026 Honda Pilot Owner's Manual: Indicator Coming On/Blinking (Malfunction Indicator Lamp) — American Honda Motor Co.
  6. Volkswagen of America bulletin V211601_2036110: Turbocharger oil supply line update — Volkswagen of America (filed with NHTSA) ,
  7. General Motors bulletin 23-NA-045: Engine RPO L3B P0299 service calibration — General Motors (filed with NHTSA) ,
  8. Saab 9-3 (2008) WIS DTC P0106 00 (T8): Manifold absolute pressure sensor circuit performance — Saab Automobile (Saab WIS service information, hosted by Saab Club of North America)
Last reviewed
Written by
Saurabh K.
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