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

P0048 Turbocharger/Supercharger Boost Control A Circuit High

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 voltage at the control output is too high, typically because of a short to battery voltage, so the actuator cannot be driven. 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

Harness chafed, short to battery voltage
Actuator coil shorted
Water in the connector
Output driver in the engine control module 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

Related codes

P0045P0046P0047P006FP0299

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