Diesel Trouble Codes

P0299 — Turbocharger/Supercharger Underboost Condition (6.7 Cummins (EGR + DPF, pre-SCR))

P0299 on 6.7 Cummins 2007.5–2012 means boost pressure is below the minimum expected for current conditions. On this platform the turbo is a Holset HE351VE VGT…

Updated September 2, 2026

What it means

Boost pressure is below the minimum expected for current conditions. On 6.7L Cummins 2007.5–2012 (EGR+DPF, pre-SCR) the turbo is HE351VE VGT with electric actuator/position sensor, no wastegate/vacuum/boost solenoid.12

Most likely causes

  1. VGT electric actuator/position sensor fault or learned travel out of range — Actuator cannot achieve commanded vane position; P2262/P226C/P0045/P0234/P0299 cluster around VGT actuator on HE351VE with electric actuator/position sensor, no wastegate/vacuum/boost solenoid.23
  2. Boost leak in intake/exhaust path — Leak downstream of compressor or upstream of turbine reduces measured boost; generic underboost definition applies.1
  3. Excessive exhaust backpressure from restricted DPF/NAC/DOC — Platform has DOC, NOx adsorber catalyst (NAC) and DPF, no SCR/DEF; restriction limits turbine drive and boost.4
  4. EGR system restriction or valve stuck open — EGR valve + cooler present on this platform; flow imbalance can lower effective boost.4
  5. MAP sensor reading error — Air metering is MAP-based; MAF is present but used for EGR/emissions, not primary fueling.4

How to diagnose

  1. Verify freeze frame and repeat under load to confirm underboost condition.
  2. Inspect intake tract, intercooler pipes, boots and clamps for leaks or damage.
  3. Check exhaust backpressure and DPF/NAC/DOC restriction; platform has DOC/NAC+DPF, no SCR/DEF.
  4. Command VGT actuator and monitor actual vs desired vane position; HE351VE uses electric actuator with position sensor, no wastegate/vacuum/boost solenoid.
  5. Check for related codes P2262/P226C/P0045/P0234 that cluster with VGT actuator faults.
  6. Inspect EGR valve operation and passages for carbon restriction; EGR valve + cooler present.
  7. Verify MAP sensor accuracy and reference; MAP is primary load sensor, MAF used for EGR/emissions.

Parts and tools you may need

Rough cost and difficulty

Cost varies by root cause; VGT actuator replacement is common on this platform. Diagnostic time is typically 1–2 hours plus parts.

When to see a pro

If bi-directional VGT control shows no response, or actuator replacement is needed, have a diesel technician perform calibration and verification. Do not attempt high-pressure fuel or turbocharger disassembly without proper training.

Sources

  1. Curated DTC seed — 6.7 Cummins (EGR + DPF, pre-SCR) (curated) ↩︎ ↩︎

  2. Curated DTC seed — 6.7 Cummins (EGR + DPF, pre-SCR) (curated) ↩︎ ↩︎

  3. Curated DTC seed — 6.7 Cummins (EGR + DPF, pre-SCR) (curated) ↩︎

  4. Curated DTC seed — 6.7 Cummins (EGR + DPF, pre-SCR) (curated) ↩︎ ↩︎ ↩︎

Watch a repair

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

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