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

P0091 Fuel Pressure Regulator A Control Circuit Low

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modePossible

On common-rail diesel and gasoline direct-injection engines, a high-pressure pump feeds the fuel rail, a sensor measures rail pressure, and the engine control module regulates it towards a target from its maps. The fuel pressure regulator A is the actuator the manufacturer designates for this: depending on the system a pressure control valve that releases fuel from the rail, or the control valve on the high-pressure pump. Some manufacturers report the pump valve under the "fuel volume regulator" codes instead. P0091 means the voltage in the control circuit is too low, typically a short to ground. Rail pressure can then no longer be controlled as intended, and the engine usually runs in reduced power.

Likely causes

Control wire shorted to ground, or connector corroded
Regulator coil faulty
Fuse or supply voltage faulty
Output driver in the engine control module faulty

Symptoms

  • Check engine light on
  • Reduced power mode
  • Hard starting or stalling

Repair estimate

DifficultyMediumDIY possible
Parts and labour€80–1,200
Time0.5–2 h

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

Parts involved

fuel pressure regulatorfuel pressure regulator wiringengine control module

Related codes

P0090P0092P0089P0087P0088

References: law.cornell.edu, saabwisonline.com, saabwisonline.com.