Diesel Trouble Codes

P226C — Turbocharger/Supercharger Boost Control A Position Exceeded Learning Limit (6.7 Cummins (SCR / DEF))

Diagnostic reference for 6.7 Cummins SCR/DEF 2013–present.

Updated September 2, 2026

What it means

The ECM has detected the VGT actuator learned travel is outside the allowable range. On this platform the Holset HE300VG VGT uses an electric actuator with integrated position sensor; there is no wastegate, vacuum control, or boost solenoid.123

Most likely causes

  1. VGT electric actuator / position sensor drift or internal fault — Actuator cannot reach or maintain learned positions; position feedback out of range. Typical for HE300VG electric actuator + integrated position sensor on 6.7 Cummins 2013–present.13
  2. VGT mechanism sticking / carbon buildup in unison ring and vanes — Mechanical binding prevents the actuator from achieving commanded travel, forcing learned limits to be exceeded. VGT is HE300VG with electric actuator, no wastegate/vacuum/boost solenoid.13
  3. Boost / intake restriction causing abnormal VGT demand — Excessive backpressure or intake restriction drives VGT to extremes, exceeding learned travel. Platform uses MAP-based load control; MAF is for EGR/emissions, not primary fueling.3
  4. ECM calibration / learned values corrupted — Learned actuator travel table is out of range due to prior fault or incomplete relearn. Generic definition: turbo actuator learned travel outside allowable range.1
  5. Wiring / connector / reference voltage issue to actuator/position sensor — Intermittent electrical fault skews position feedback, causing learned limit exceedance. Electric actuator + integrated position sensor is the control method on this platform.13

How to diagnose

  1. Verify code and freeze frame; confirm P226C is active and note engine speed, load, coolant temp at set.
  2. Inspect turbocharger intake and exhaust for restriction; check air filter, intake piping, intercooler, and DPF/SCR backpressure indicators. Platform has DOC/DPF and SCR/DEF; restriction can drive VGT to limits.
  3. Command VGT actuator through scan tool and monitor desired vs actual position and learned travel limits. Compare to spec; look for inability to reach min/max or position error. Electric actuator + integrated position sensor, no wastegate/vacuum/boost solenoid.
  4. Check actuator and position sensor supply/reference/ground circuits and connector for corrosion, oil intrusion, or damage. Verify signal integrity during sweep.
  5. Inspect VGT mechanism for sticking/carbon via borescope or actuator response test; look for slow or non-linear movement indicating unison ring/vane binding. HE300VG VGT with electric actuator.
  6. Review related boost codes P2262, P0234, P0299 for under/overboost context; MAP-based load control on this platform.
  7. If mechanical and electrical checks pass, evaluate ECM learned values and perform actuator relearn per manufacturer procedure; confirm learned travel returns within limits. Generic definition is learned travel outside allowable range.

Parts and tools you may need

Rough cost and difficulty

Parts and labor vary by model year and configuration. 2013–2018 and 2021+ use CP3; 2019–2020 use CP4.2. Always confirm hardware per VIN before ordering.

When to see a pro

If diagnosis indicates internal turbocharger mechanical failure, high-pressure fuel system concerns, or requires removal/replacement of safety-critical components, have a qualified diesel technician perform inspection and repair. Do not attempt step-by-step repair of high-pressure fuel or turbocharger on public roads.

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) ↩︎ ↩︎ ↩︎ ↩︎ ↩︎