P0299: How to Diagnose & Fix — Turbo/Supercharger Underboost Condition
121 vehicles · 31 makes · $50-$15,000 repair
How to diagnose and fix P0299: most-reported vehicles
Ranked by owner reports. Each card gives the symptoms, how to confirm the cause, the fix, parts and sources for that vehicle.
Toyota Tundra · 2022–2023
Toyota recalled approximately 98,568 Tundras with the new 3.4L twin-turbocharged V6 engine due to machining debris left in the engines during production. This debris can damage the crankshaft bearings, leading to engine knock, rough running, no-start conditions, and sudden loss of power while driving at highway speeds.
Common Symptoms
- Engine knocking noise
- Rough engine running
- Engine stalling
- No-start condition
- Sudden power loss at speed
- Check engine light
How to Fix
Toyota will inspect and replace affected engines under recall free of charge. Engine replacement is the primary remedy. Owners experiencing symptoms should stop driving immediately and contact Toyota.
Owner tips & cautions
- WarningThis is a high-severity issue - ignoring it can lead to costly repairs or safety concerns. Address it promptly.
- TipGet a proper diagnosis before replacing parts - similar symptoms can have different causes
- TipSearch Toyota Tundra forums and owner groups for real-world experiences and DIY guides
- TipGet multiple quotes from independent mechanics - dealer prices can be 2-3x higher for the same repair
Sources for this issue (3)
Volvo S40 · 2004–2012
The PCV (positive crankcase ventilation) system on the S40/V50 2.5L T5 engine is a well-known failure point. The system uses a complex oil separator and breather box that clogs with oil sludge, causing excessive crankcase pressure. This pressure forces oil past every seal in the engine - rear main seal, valve cover gaskets, oil filter housing, and turbo seals. Left unchecked, the crankcase overpressure can push the rear main seal out, causing catastrophic oil loss. The PCV system should be treated as a maintenance item on these engines. The issue affects all P1 platform Volvos including S40, V50, C30, and C70.
Common Symptoms
- Oil leaks from multiple locations simultaneously
- Rough idle and misfires
- Whistling noise from engine bay (vacuum leak through PCV)
- Check engine light with lean codes (P0171)
- Oil pooling on top of transmission (rear main seal leak)
- White smoke from exhaust (oil in intake)
How to Fix
Replace the entire PCV system including oil trap/separator (Volvo part 31338023), breather hoses, and PCV valve. This is a $100-200 parts job but 3-4 hours labor due to the system's location behind the intake manifold. Replace any damaged seals (rear main seal, valve cover gasket) that leaked due to excessive pressure. Clean intake manifold of oil deposits. Prevention: replace PCV system every 80,000-100,000 miles. Use an OEM or Mann+Hummel PCV unit - cheap aftermarket units fail quickly.
What you need to fix it
Only diagnosis- and fitment-reviewed repair parts are linked here.
- IPD 140064 early non-PTC P1 oil-separator diaphragm
replace a confirmed torn diaphragm in a serviceable early non-PTC oil-filter-housing separator Fitment/availability: 2004.5-2005 P1 Volvo S40 five-cylinder through engine serial 3285661 with the original non-PTC oil-separator box; inspec…
- IPD 142641 later PTC-style P1 five-cylinder PCV diaphragm, cap and spring kit
replace a confirmed torn diaphragm in a serviceable later PTC-style oil-filter-housing separator Fitment/availability: 2006-up P1 Volvo S40 2.4i/T5 and 2004.5-2005 from engine serial 3285662 or an earlier car updated to the PTC-style hou…
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RAM 3500 · 2013–2025
The RAM 3500 6.7L Cummins equipped with the integrated exhaust brake system experiences failures of the VGT (Variable Geometry Turbocharger) actuator and exhaust brake solenoid. The exhaust brake uses the VGT turbo vanes to create backpressure for engine braking while towing. The electronic actuator (Holset HE351VE/HE300VG) sticks or fails due to carbon buildup, causing loss of exhaust brake function, reduced turbo performance, limp mode, and DTC codes P2263 or P006A. TSB 14-001-21 addresses VGT actuator calibration. Actuator replacement costs $800-1,500; complete turbo replacement is $2,500-4,000.
Common Symptoms
- Exhaust brake not engaging or weak braking effect
- Check engine light with turbo codes (P2263, P006A, P0299)
- Reduced engine power / limp mode
- Black smoke from exhaust under acceleration
- Turbo whistle or surge at idle
- Slow turbo spool-up / turbo lag
- Exhaust brake light blinking
How to Fix
For sticking actuator: Remove and clean the VGT actuator and turbo vanes of carbon deposits. Actuator exercise procedure via wiTECH can help prevent sticking. Check TSB 14-001-21 for actuator calibration procedure. If the actuator motor is failed, replace the electronic actuator assembly ($800-1,500, Holset 5497296 or 5610723). If turbo vanes are severely carboned or damaged, complete turbo replacement is needed ($2,500-4,000). Regular highway driving helps keep vanes clean; trucks that idle excessively build up carbon faster.
MINI Cooper S · 2007–2013
Mercedes-Benz Sprinter · 2007–2018
Find P0299 by make
Browse every documented model and issue for your make.
P0299 code reference
General diagnostic-code context. The code alone does not confirm a cause for your vehicle; use the applicable issue card and its sources.
Frequently asked questions
What does P0299 mean?
P0299 stands for "Turbo/Supercharger Underboost Condition." P0299 means the engine computer detected an underboost condition — the turbocharger or supercharger is producing less boost pressure than the PCM expects for the given conditions. The computer compares the manifold/boost pressure sensor reading to a target based on engine load, and when actual boost falls short, it sets this code. The most common real-world cause is a leak somewhere in the intake/charge-air path. You'll typically feel reduced power or sluggish acceleration, and the engine may go into a reduced-power mode.
What are the most common causes of P0299?
The most common causes of P0299 are: Boost/intake leak (cracked or loose charge-air hose or intercooler), Faulty or sticking turbo wastegate or actuator, Stuck or clogged variable-geometry turbo vanes (VGT), Faulty boost pressure or MAP sensor, Leaking or disconnected vacuum/boost control lines, Restricted air intake or clogged air filter, Failed boost control solenoid, Worn or failing turbocharger. The specific cause varies by vehicle.
How much does it cost to fix P0299?
Repair costs for P0299 range from $50 to $15,000, depending on the vehicle and root cause.
Which vehicles are affected by P0299?
Au7o has documented P0299 across 121 vehicle models from 31 manufacturers: Acura, Audi, BMW, Buick, Cadillac, Chevrolet, Chrysler, Citroen, Dodge, Fiat, Ford, GMC, Honda, Hyundai, Jeep, Kia, Land Rover, MINI, Mazda, Mercedes-Benz, Nissan, Opel, Peugeot, Porsche, RAM, Renault, Saab, Subaru, Toyota, Volkswagen, Volvo.
Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.