P00AF — Turbocharger/Supercharger Boost Control A Module Performance — 6.7 Cummins (SCR / DEF)
Diagnostic reference for 6.7 Cummins SCR/DEF 2013-present. Focus on VGT actuator module performance, power/ground/data integrity, and vane/actuator mechanical…
What it means
Generic definition: turbo boost control (VGT actuator) module is not performing as expected. On 6.7L Cummins HE300VG the VGT uses an electric actuator with integrated position sensor; no wastegate/vacuum/boost solenoid.12
Most likely causes
- VGT electric actuator module internal failure or degraded position sensor — Actuator electronics or integrated position sensor drift/failure causes module performance error and slow response. Commonly reported as a recurring failure on this platform affecting boost build and exhaust brake function.34
- Actuator power/ground or data wiring fault — Loss/corrosion/intermittent supply or ground, or CAN/data wiring to the actuator module triggers performance codes. Check harness, connectors, and chafing near turbo.1
- Sooted/sticking VGT vanes or unserviceable turbocharger — Carbon buildup or vane sticking prevents commanded vane position from being achieved, leading to module performance detection. Typical on HE300VG with electric actuator.1
- Boost/exhaust leaks or intake restrictions affecting closed-loop control — Leaks at boots, intercooler, EGR connections, or intake restriction cause actual boost to diverge from commanded, contributing to module performance detection.2
How to diagnose
- Verify code P00AF active and freeze-frame conditions; confirm no related under/overboost codes P0299/P0234 present.
- Inspect VGT actuator connector and wiring for corrosion, oil intrusion, chafing; check power/ground supply and data line integrity to the actuator module.
- Command VGT vane sweep with scan tool and monitor desired vs actual vane position feedback; look for slow response, limited travel, or position sensor rationality faults.
- Inspect turbocharger inlet/exhaust for excessive soot, oil, or debris; check for vane sticking or actuator rod binding; assess actuator mechanical movement without disassembly.
- Check boost system integrity: pressure-test charge air system, inspect intercooler boots and clamps, verify MAP sensor readings vs expected boost under load.
- Review recent regen history and exhaust backpressure; excessive soot loading can contribute to vane sticking on HE300VG.
Common mistake to avoid
Skipping the VGT actuator calibration. The 6.7 Cummins Holset actuator has to be relearned with a scan tool after it is replaced or disconnected, or boost control will stay off. Source: OBDAdvisor — diesel limp mode diagnosis.
Parts and tools you may need
- Scan tool with Cummins enhanced diagnostics and bi-directional VGT control
- Digital multimeter
- Wiring diagram for VGT actuator power/ground/data
- Boost pressure test kit
- Inspection mirror and borescope
Tools you’ll need
- bi-directional scan tool — Commands VGT vane sweep and compares desired vs actual position feedback to detect actuator or sensor rationality faults.
- digital multimeter — Checks actuator power, ground, and data line integrity for corrosion or wiring faults at the VGT connector.
- boost pressure test kit — Pressure-tests the charge air system to rule out boost leaks that can cause closed-loop VGT control errors.
- borescope — Inspects turbocharger inlet/exhaust and VGT vane condition for soot buildup or sticking without full disassembly.
Rough cost and difficulty
| Likely repair | Parts | Shop labor | Who usually does it |
|---|---|---|---|
| Wiring or connector repair | $10–$100 | 1–4 hrs | DIY with tools and a manual |
| Intercooler boot, clamp or pipe repair | $20–$200 | 0.5–2 hrs | Easy DIY |
| Electronic VGT actuator (needs calibration) | $500–$1,400 | 1–2 hrs | DIY with tools and a manual |
| Turbocharger | $1,500–$3,500 | 3–6 hrs | Shop |
Typical US independent-shop figures; labor runs about $120–$180 per hour (dealers charge more). Confirm the diagnosis before buying parts.
When to see a pro
If bi-directional control shows no vane movement, position feedback is erratic, or wiring tests pass but performance persists, professional evaluation of the HE300VG turbocharger and actuator module is warranted. High-pressure fuel or turbocharger internal service requires specialist tools and safety precautions.
Check for recalls
Recalls are tied to your truck’s VIN, so check yours directly: enter the VIN at NHTSA’s recall lookup. Open safety recalls are repaired free at a dealer.
Sources
Repair videos: P00AF on the 6.7 Cummins '13+
Third-party videos, not ours — picked for this engine. Confirm anything against the factory service information for your truck.
Spotted an error, or something missing? Tell us
Run a 6.7 Cummins (SCR / DEF)? This goes straight to the editor — it is not published.