P0299 on Chevrolet
Turbo/Supercharger Underboost Condition
P0299 on Chevrolet vehicles indicates turbo/supercharger underboost condition. Au7o has documented this code across 4 Chevrolet models — most commonly on Silverado 1500, Sonic, Trailblazer. 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. Typical repair costs on Chevrolet range from $150 to $2,500, depending on the specific model and root cause.
Common Causes of P0299
- •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
P0299 on Chevrolet by Model
Chevrolet Silverado 1500(1 issue)
- 2.7L Turbomax (L3B) Cold-Start Rattle and Wastegate Actuator Wear2019-2024
The turbocharged 2.7L Turbomax four-cylinder develops a metallic rattle/knock on cold start-up, most pronounced in the first few seconds before oil pressure builds. The root cause is premature wear in the turbocharger wastegate linkage/actuator, which can also throw a turbo-underboost code. Owners also report VVT camshaft-actuator (CPAS) solenoid faults and engine-harness chafing on this engine. Because the L3B is direct-injection only (no port injection), intake-valve carbon buildup compounds the rough-idle/misfire complaints as miles accumulate.
Chevrolet Sonic(1 issue)
- 1.4L Turbo PCV Valve Cover Diaphragm Failure2012-2020
The 1.4L turbocharged Ecotec engine in the Sonic shares the notorious PCV system failure with the Chevrolet Cruze. The PCV regulator diaphragm integrated into the valve cover ruptures, causing massive vacuum leaks. Additionally, the intake manifold check valve (small red/orange valve) fails, compounding the issue. This affects virtually all 1.4T Sonics eventually, typically between 50,000-100,000 miles.
Chevrolet Trailblazer(1 issue)
- Turbocharger Oil Leak and Failure2021-2026
The 1.2L and 1.3L turbocharged three-cylinder engines in the Trailblazer can develop turbo oil seal leaks, causing oil consumption and blue smoke on startup. The turbo oil feed and return lines are also prone to seepage. In severe cases, the turbo can fail completely.
Chevrolet Trax(2 issues)
- 1.4L Turbo Wastegate Actuator Failure2014-2020
The 1.4L turbocharged engine in the Trax (shared with Cruze, Sonic, and Buick Encore) develops wastegate actuator failures. The wastegate seal degrades, allowing exhaust gases to bypass the turbine wheel and reduce boost. The wastegate actuator arm design has a known mechanical weakness. GM TechLink bulletin noted many returned turbochargers had no fault and emphasized proper diagnosis before replacement.
- 1.4T Ecotec Turbo and Coolant Issues2015-2022
The Trax uses the same 1.4T Ecotec engine as the Cruze with similar issues: turbo oil feed line leaks, PCV system failures, and coolant system plastic component cracking. The coolant outlet/thermostat housing is the most common failure point.
Looking for P0299 on a different make?
View P0299 across all makes →Frequently Asked Questions
What does P0299 mean on Chevrolet?▼
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. On Chevrolet specifically, this code is documented across 4 models.
What causes P0299 on Chevrolet vehicles?▼
Common causes on Chevrolet: 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. Specific causes vary by model and year — see the per-model sections below.
How much does it cost to fix P0299 on a Chevrolet?▼
Repair costs on Chevrolet range from $150 to $2,500, depending on the specific model and root cause.
Which Chevrolet models have P0299 documented?▼
Au7o has documented P0299 on 4 Chevrolet models: Silverado 1500, Sonic, Trailblazer, Trax.