Diesel Trouble Codes

P0299 — Turbocharger/Supercharger Underboost Condition (6.7 Power Stroke)

P0299 on 6.7 Powerstroke means boost pressure is below the minimum expected for current conditions. Diagnose by confirming underboost, then checking the most…

Updated September 1, 2026

What it means

Boost pressure is below the minimum expected for current conditions.1

Most likely causes

  1. Charge-air-cooler (intercooler) boot leaks — Inspect intercooler boots and clamps for splits, oil seepage, or loose connections that bleed boost. Typical on this platform.1
  2. VGT vanes stuck open — VGT vanes stuck open reduce drive pressure; typical cause of underboost on this platform.1
  3. Sticking turbo actuator — A sticking or slow VGT actuator prevents proper vane positioning; typical on this platform.1
  4. Restricted air filter — A clogged air filter limits inlet flow and reduces achievable boost; typical on this platform.1
  5. VGT vane sticking from soot — Soot buildup can cause VGT vane sticking leading to boost performance deviation; typical on this platform.2
  6. Turbo actuator fault — Actuator electrical/mechanical fault can cause actual boost to not track desired boost; typical on this platform.2
  7. MAP/boost sensor error — Erroneous boost sensor readings can cause underboost detection; typical on this platform.2
  8. Turbo actuator learned travel out of range — Actuator learned travel outside allowable range indicates sticking VGT mechanism or worn/failed actuator; sometimes clears after a successful relearn.3

How to diagnose

  1. Verify code and freeze-frame conditions; confirm underboost with live data vs desired boost.
  2. Inspect intake and charge-air system for leaks: intercooler boots, CAC pipes, and clamps. Typical leak points for P0299 on this platform.
  3. Check air filter restriction and intake blockage.
  4. Review VGT actuator command vs actual position data; look for slow response or limited travel.
  5. Assess MAP/boost sensor plausibility and wiring; compare to barometric and ambient readings.
  6. If VGT sticking is suspected, evaluate for soot-related vane sticking per platform patterns.
  7. Check for learned actuator limits; a position exceeded learning limit suggests sticking VGT or actuator wear.

Parts and tools you may need

Rough cost and difficulty

Cost varies by root cause; boot replacement is low cost, VGT/turbo service is higher. Diagnosis should confirm the specific fault before parts replacement.

When to see a pro

If VGT mechanism is stuck, turbocharger requires removal and service. High-pressure fuel and turbo work involve safety risks; have a qualified diesel technician perform diagnosis and repairs.

Sources

  1. Curated DTC seed — 6.7 Powerstroke (curated) ↩︎ ↩︎ ↩︎ ↩︎ ↩︎

  2. Curated DTC seed — 6.7 Powerstroke (curated) ↩︎ ↩︎ ↩︎

  3. Curated DTC seed — 6.7 Powerstroke (curated) ↩︎

Watch a repair

Third-party videos, not ours — for illustration. Confirm anything against the factory service information for your truck.

P0299 Trouble Code – Don’t Replace Your TURBO Yet! — 8020 Automotive

Causes and Fixes P0299 Code: Turbo / Supercharger Underboost Condition — HVAC Mechanic