Powertrain, generic · Fuel and air metering, auxiliary emission controls

P0045 Turbocharger/Supercharger Boost Control A Circuit/Open

Check engine lightOn

EmissionsRelevant

Drive cycleRequired

Limp modePossible

"Boost control A" is the electrically driven actuator the engine control module uses to set boost pressure: depending on the engine a pulse-width modulated solenoid or vacuum converter at the wastegate, the control valve of variable turbine vanes, or an electric actuator with position feedback. The letters A and B denote two separate actuators, for example on the low- and high-pressure turbocharger of a two-stage system, not the cylinder banks. This code is set when the control circuit is open: with the driver switched off no load can be measured, or the measured state does not match the command. Without control the actuator usually falls back to its rest position, which on most engines means low boost; depending on the design too much boost is also possible.

Likely causes

Connector at the actuator corroded or loose

Wire broken or chafed through

Solenoid coil in the actuator burnt out

Fuse or ignition supply faulty

Engine control module or separate actuator control unit faulty

Symptoms

Check engine light on
Loss of power or reduced power mode
Weak acceleration, noticeable turbo lag
Overboost possible in rare cases

Repair estimate

DifficultyMediumDIY possible

Parts and labour€50–900

Time0.5–2.5 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

boost control actuator aboost control actuator wiringengine control module

References: law.cornell.edu, gsi.ext.gm.com, saabwisonline.com, saabwisonline.com.