P0299: Turbocharger / Supercharger 'A' Underboost Condition
The ECM compares actual manifold boost pressure (MAP sensor) against commanded target boost pressure. If boost pressure is lower than target by more than 3–5 psi for more than 5 seconds under wide-open throttle, P0299 is set.
Driveability & Safety Advisory
Drivable in reduced power mode. Acceleration will feel sluggish and gutless, especially uphill.
Official Manufacturer TSB Advisories
Factory Condition: Turbocharger diverter valve (DV) rubber diaphragm tears, leaking boost back into compressor inlet.
Factory Condition: Turbocharger internal wastegate shaft arm wears loose, causing wastegate flapper to rattle and leak boost.
Physical Component Location & Service Access
Turbocharger is bolted directly to the exhaust manifold. Charge air cooler (intercooler) is mounted behind front bumper grille.
Electrical Specifications & Live PID Benchmarks
Scan Tool Live Data Targets
Digital Multimeter (DMM) Specs
Documented Model-Specific Case Studies
Root Cause: Wastegate flapper valve seat cracked inside turbine housing.
Verified Fix: Replace turbocharger assembly.
Technician Inspection & Testing Workflow
Visual and tactile check: Inspect every rubber intercooler charge pipe hose clamp from turbo compressor outlet through front intercooler up to the throttle body. Look for blown-off boots or split silicone.
Test diverter valve: Remove blow-off / diverter valve. Check rubber membrane for tears.
Check wastegate actuator arm: Wiggle wastegate linkage by hand. If loose and sloppy, the flapper door cannot seal.
Perform boost leak pressure test using an air compressor adapter set to 15 psi.
Recommended Diagnostic Tools & Verified Parts
BlueDriver Bluetooth Pro OBDII Scan Tool
Wireless sensor telemetry & enhanced diagnostics (Engine, ABS, Airbag). Delivers verified vehicle repair reports.
Autel AutoLink AL519 / AL319 OBD2 Scanner
Color screen standalone scanner. One-click I/M emissions readiness status, freeze-frame data, live DTC reset.
AstroAI Digital Multimeter 6000 Counts TRMS
Auto-ranging multimeter for measuring sensor pin resistance (ohms), live DC bias voltage, and circuit continuity per OEM specs.
As an Amazon Associate, AutoFixCodes earns from qualifying purchases.
Cost Breakdown
Tools & Parts Matrix
Diagnostic Questions & Answers
Does P0299 always mean I need a new turbocharger?
No! Over 50% of underboost codes are caused by simple boost leaks: a loose hose clamp on the intercooler piping, a cracked plastic pipe, or a torn $45 diverter valve.