P0299 on Cadillac
Turbo/Supercharger Underboost Condition
P0299 on Cadillac vehicles indicates turbo/supercharger underboost condition. Au7o has documented this code across 2 Cadillac models — most commonly on CT6, XT4. 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 Cadillac range from $200 to $6,500, 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 Cadillac by Model
Cadillac CT6(1 issue)
- 3.0L Twin-Turbo (LGW) Turbocharger Turbine Wheel Failure — GM Service Update 174082016-2018
GM issued Service Update 17408 covering 2016-2018 Cadillac CT6 sedans built with the 3.0L V6 twin-turbo (RPO LGW) after turbochargers were found capable of shedding turbine-wheel material. Owners report a whistle, siren or grinding noise from the turbo area followed by a hard loss of boost and a check-engine light. Because the LGW runs two small turbos, a single failed unit can drop the car into reduced power while the other side still spools, which is why the complaint is usually described as 'sudden loss of power under acceleration' rather than a no-start. Metal debris from a disintegrating turbine wheel can be drawn downstream, which is what turns a turbo replacement into an engine replacement in the worst cases. This is specific to the LGW twin-turbo — the 2.0L four and the naturally aspirated 3.6L LGX in the same body do not share it.
Cadillac XT4(1 issue)
- 2.0T LSY Engine - PCV and Turbo Coolant Line Issues2019-2025
The XT4 uses the 2.0T LSY engine which is an evolution of the LTG found in the ATS/CTS. The LSY has improved reliability but shares some issues including PCV system problems and turbo coolant line leaks. The turbo coolant lines can develop leaks at the connections, causing coolant loss and potential turbo damage from overheating. The PCV valve/cover can fail causing oil consumption. These issues typically appear between 40,000-80,000 miles.
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View P0299 across all makes →Frequently Asked Questions
What does P0299 mean on Cadillac?▼
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 Cadillac specifically, this code is documented across 2 models.
What causes P0299 on Cadillac vehicles?▼
Common causes on Cadillac: 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 Cadillac?▼
Repair costs on Cadillac range from $200 to $6,500, depending on the specific model and root cause.
Which Cadillac models have P0299 documented?▼
Au7o has documented P0299 on 2 Cadillac models: CT6, XT4.