P226B: Turbocharger/Supercharger A Boost Pressure Too High - Mechanical

P226B reports boost from turbocharger or supercharger A rising too high for a mechanical reason, for instance a wastegate or bypass that will not open or a seized actuator linkage, rather than a sensor or wiring fault. VW's 2014 book for the supercharged Touareg 3.0 TSI sets it when boost passes 250 kPa. GM uses the code only for European calibrations: its 2018 diesel tables list P226B as an EOBD code in the boost-system fault groups, while the US software maps the same fault group to P2263. CARB requires boosted engines to detect overboost. Where P0234 judges a deviation above the target, P226B points to a mechanical cause; P2262 describes boost that does not appear at all. To protect the engine the ECM usually reduces torque, and some engines open a relief path.

Symptoms

• Sudden power cut or reduced-power mode under load
• MIL on
• Unusually strong surge of power just before the cut

Most likely causes

• Wastegate flap seized closed by corrosion or carbon
• Seized or misadjusted wastegate or VGT actuator linkage
• Vacuum or pressure line to a pneumatic actuator leaking or blocked
• Supercharger bypass valve not opening

What to check, in order

Start with the simplest. You can tick off each step.

1. Check the hoses, clamps, and intercooler
2. Check the sensor's ground and make sure the signal wire is not receiving voltage from another circuit.
3. Compare commanded and actual pressure in live data
4. Check the actuator's movement
5. Check the vacuum hoses and the solenoid valve
6. Check the oil and the turbo shaft play before replacing it

Good to know

• Repair difficulty: hard
• It can trigger limp mode.
• It affects emissions.

What each character of P226B means

• P: Powertrain: engine and transmission
• 2: Generic code: same on every make
• 2: Fuel injection
• 6B: Specific fault in that system

Frequently asked questions

Can I keep driving with code P226B?

Drive without demanding power and go to a repair shop soon. If you see a lot of blue smoke or hear a metallic noise, shut off the engine.

What causes code P226B?

The most common causes are: wastegate flap seized closed by corrosion or carbon; seized or misadjusted wastegate or VGT actuator linkage; vacuum or pressure line to a pneumatic actuator leaking or blocked.

Related codes

• P0234Turbocharger/Supercharger A Overboost Condition
• P2262Turbocharger/Supercharger Boost Pressure A Not Detected - Mechanical
• P2263Turbocharger/Supercharger A Boost System Performance
• P0299Turbocharger/Supercharger A Underboost Condition
• P0243Turbocharger/Supercharger Wastegate Actuator A

Sources

• static.nhtsa.gov: MC 10119356 9999
• gsi.ext.gm.com: 18OBDG04 Engine Diagnostics
• law.cornell.edu: 13 CCR 1968.2

Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.