Turbo/Super Charger Underboost
The DURAMAX-P0299 (Duramax) diesel fault code means: Turbo/Super Charger Underboost. This is a serious severity code.
- Keep driving?
- No — stop driving
- DIY difficulty
- advanced
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What Are the Symptoms of DURAMAX-P0299?
- Check Engine Light on
- Loss of power, especially under load
- Reduced power mode
What Causes DURAMAX-P0299? (Most Likely First)
- Boost leak from a loose clamp, split hose or cracked charge pipe High
- Sticking turbocharger control mechanism Moderate
- Boost control solenoid or actuator fault Moderate
- Boost pressure sensor reading low Low
Can I Still Drive with DURAMAX-P0299?
No — stop driving. DURAMAX-P0299 is rated serious severity. Continuing to drive in this state risks further damage — get it looked at before your next trip.
Common Fixes by Vehicle
What techs usually find when diagnosing DURAMAX-P0299 on specific platforms — tap a platform for the fix and the exact part:
2006-2010 GMC/Chevy 2500/3500 6.6L LBZ/LMM Duramax Advanced DIY
P0299 (turbo underboost) on the LBZ/LMM is usually a stuck VGT vane assembly from soot buildup. A turbo clean with ATF and a good highway run sometimes frees it; otherwise the turbo must be removed and the unison ring cleaned or replaced. Budget 6-8 hours shop labor. An aftermarket non-VGT turbo (like the PPE Performance turbo) is a common delete for off-road applications.
Labor: 6-10 hours2011-2016 GMC/Chevy 2500/3500 6.6L LML Duramax Moderate DIY
On the LML, P0299 often pairs with low boost complaints and is caused by a leaking intake boot or cracked charge pipe. Pressure-test the intake first -- budget $30-$80 for a silicone boot replacement. If intake is tight, the VGT actuator is next; OEM actuator is $500-$900 installed.
Labor: 1-3 hoursFrequently Asked Questions
What does P0299 mean on a Duramax?
P0299 means Turbo/Super Charger Underboost. Measured boost pressure is lower than the engine computer is asking for.
Is P0299 a Duramax-specific code?
No. P0299 is a generic OBD-II code defined by SAE J2012, so it means the same thing on any vehicle that sets it. The exact conditions GM uses to set it on its diesels are in GM service information.
Mechanics Guide Step-by-step diagnosis
How Do You Diagnose DURAMAX-P0299?
Pressure-test the intake and charge air system for leaks.
Compare commanded and actual boost on a scan tool under load.
Check for boost control and boost sensor codes, and fix those first.
Sources 1
This page is built from documented references. Verify against your own service info before repair work.
- SAE J2012Diagnostic Trouble Code Definitions (defines P0299 as a generic OBD-II code)
P0299 on Other Platforms
The same code ID appears across other engines, vehicles, and equipment. Diagnostic flow varies by platform — see the matching breakdown:
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