P0249: Turbocharger/Supercharger Wastegate Actuator B Low

What does P0249 mean?

The wastegate lets exhaust bypass the turbine to limit boost; actuator B is either a pulse-width-modulated solenoid on a pneumatic wastegate can or an electric actuator with a position sensor. B is the second turbo or actuator, so B codes only exist on engines with two. P0249 means the control circuit of actuator B reads low, typically the control wire shorted to ground. On GM's LGW twin-turbo less than 0.5 Ω to ground with the driver off in 10 of 20 samples sets it with the warning light in the first trip; older GM modules need two trips. Ford reports it on pneumatic wastegates after 2–3 s. Boost control is then switched off and only the spring-set base boost remains – less power, but no risk of overboost.

The code tells you which monitor failed, not which part is broken. Test before replacing parts.

Symptoms

• Check engine light on
• Clearly less power, boost only at base level
• Uneven boost between the turbos
• Reduced engine power message possible

Common causes

• High Control wire of wastegate B chafed through to ground
• Medium Valve or actuator winding B shorted
• Medium Connector damage or moisture
• Low Driver stage in the engine module faulty

Likelihood is a general estimate across vehicles; your make and model may differ.