Powertrain, generic · Auxiliary emission controls

P04FD EGR Actuator A Control Processor Performance

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modePossible

Exhaust gas recirculation (EGR) routes part of the exhaust back into the intake to lower combustion temperature and NOx. Some EGR actuators have their own electronics (smart actuators), with position control inside the actuator and communication with the engine module by bus or PWM. P04FD means the actuator reports an internal processor or electronics fault, or its self-test failed. CARB does not require such internal faults to be reported, so the code is a voluntary detail. Volvo and Mack trucks with turbocompound document it with false triggers fixed by engine software. The actuator then goes to its default position and EGR is off.

Likely causes

Engine or actuator software (false trigger)
Electronics in the EGR actuator faulty (heat, moisture)
Actuator supply or ground unstable
Valve stiff, causing a control fault in the actuator

Symptoms

  • Check engine light on
  • Reduced power possible
  • Higher NOx

Repair estimate

DifficultyHardWorkshop job
Parts and labour€100–1,500
Time0.5–4 h

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

Parts involved

egr actuator aegr actuator electronicsengine control module

Related codes

P04FAP0403P0404P049DP0489P0490

References: static.nhtsa.gov, law.cornell.edu.