Diesel Trouble Codes

P0234 — Turbocharger/Supercharger Overboost Condition (6.7 Cummins (EGR + DPF, pre-SCR))

P0234 on 6.7 Cummins 2007.5–2012 EGR+DPF pre-SCR means the ECM has detected boost pressure above the allowed maximum for current conditions. On this platform…

Updated September 2, 2026

What it means

Boost pressure has exceeded the maximum allowed for current conditions. On this platform the turbo is a Holset HE351VE VGT with an electric actuator/position sensor and no wastegate/vacuum/boost solenoid.12

Most likely causes

  1. VGT actuator over-travel / learned position out of range — Electric VGT actuator sticks or learns beyond limits, causing vanes to close too far and over-boost. This platform’s VGT actuator is a common failure and is linked to P2262/P226C/P0045/P0234/P0299.23
  2. VGT vane mechanism sticking / carbon buildup — Soot/carbon in the HE351VE unison ring/vanes causes the vanes to stay closed, raising boost. Actuator-related codes cluster around this hardware.23
  3. Boost pressure sensor / MAP signal error — Erroneous MAP reading can falsely indicate overboost. Air metering is MAP-based on this platform.1
  4. Intake restriction / EGR system fault causing abnormal boost — Restricted intake, clogged air filter, or EGR valve/cooler issues can alter boost control. Platform has EGR valve + cooler, DOC/NAC+DPF, no SCR/DEF.1
  5. ECM calibration / learned adaptation issue — Incorrect learned VGT travel limits or calibration drift can set overboost. P226C specifically references learned travel out of range.2

How to diagnose

  1. Verify freeze-frame conditions for engine speed, load, and actual vs desired boost.
  2. Inspect intake system for restrictions and check air filter condition.
  3. Check MAP sensor reading vs a calibrated gauge under load.
  4. Command VGT vane position with a scan tool and monitor actual vs desired position and actuator feedback.
  5. Inspect VGT actuator operation, linkage, and for carbon binding in the unison ring/vanes.
  6. Review related codes P2262, P226C, P0045, P0299 for actuator/electrical issues.
  7. Check EGR valve operation and intake path for excessive soot buildup.
  8. Clear adaptations and perform VGT relearn per OEM procedure, then retest under load.

Parts and tools you may need

Rough cost and difficulty

Diagnostic labor varies; VGT actuator replacement is a common repair on this platform and typically exceeds inspection labor. Parts and labor depend on extent of carbon buildup or turbo replacement needed.

When to see a pro

If overboost persists after electronic checks, or if turbo disassembly/cleaning or actuator replacement is required, have a qualified diesel technician service the HE351VE VGT assembly. Do not attempt high-pressure fuel or turbocharger internal repairs without proper training and safety controls.

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) ↩︎ ↩︎

Watch a repair

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

Fixing Stuck 6.7 Turbo Vanes — KC TURBOS · 125K views

P0234 Code: Turbo Boost Out of Control? — 8020 Automotive · 17K views

Causes and Fixes P0234 Code: Turbocharger / Supercharger Overboost Condition — HVAC Mechanic · 229K views