Diesel Trouble Codes

P0234 — Turbocharger/Supercharger Overboost Condition (6.7 Cummins (SCR / DEF))

Diagnostic reference for 6.7L Cummins SCR/DEF 2013–present. If sources do not support a point, omit it. Rank causes most-likely first.

Updated September 2, 2026

What it means

The ECM has detected boost pressure exceeding the maximum allowed for current conditions on a 6.7L Cummins with Holset HE300VG VGT, 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 — On this platform the turbo is HE300VG VGT with electric actuator + integrated position sensor; no wastegate/vacuum/boost solenoid. Actuator position errors can cause over-boost. Related platform codes include P226C for actuator learned travel exceeded.21
  2. VGT vane mechanism sticking / carbon buildup causing over-boost — VGT vane sticking can prevent proper vane control, leading to boost exceeding target. Platform uses HE300VG VGT with electric actuator + position sensor; no wastegate/vacuum/boost solenoid.21
  3. Boost pressure sensor / MAP sensor reading error — Boost control is MAP-based load control on this platform; erroneous MAP/boost sensor input can cause over-boost detection. Air metering is MAP-based; MAF is for EGR/emissions, not primary fueling.3
  4. Intake restriction / exhaust backpressure anomaly affecting boost control — Underboost/overboost conditions are linked to turbocharger, boost control, intake on this platform.3
  5. ECM calibration / learned values drift — Turbo actuator learned travel issues are described for this platform, e.g., P226C position exceeded learning limit.2

How to diagnose

  1. Verify code and freeze frame; confirm P0234 present on 6.7L Cummins SCR/DEF 2013–present with HE300VG VGT electric actuator.
  2. Inspect for intake/exhaust restrictions and boost leaks; platform is MAP-based with VGT electric actuator, no wastegate/vacuum/boost solenoid.
  3. Check turbo actuator operation and position sensor feedback; platform uses electric actuator + integrated position sensor; no wastegate/vacuum/boost solenoid.
  4. Review related turbo codes P2262, P226C, P0045, P0299 for pattern.
  5. Assess MAP/boost sensor readings vs. expected under controlled conditions; air metering is MAP-based; MAF used for EGR/emissions, not primary fueling.

Parts and tools you may need

Rough cost and difficulty

Parts and labor vary by model year and configuration; obtain quotes for specific VIN.

When to see a pro

If diagnosis involves high-pressure fuel system or safety-critical systems, have a qualified diesel technician perform inspection. Do not attempt step-by-step repair of safety-critical systems.

Sources

  1. Curated DTC seed — 6.7 Cummins (SCR / DEF) (curated) ↩︎ ↩︎ ↩︎

  2. Curated DTC seed — 6.7 Cummins (SCR / DEF) (curated) ↩︎ ↩︎ ↩︎ ↩︎

  3. Curated DTC seed — 6.7 Cummins (SCR / DEF) (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