Powertrain, generic · Auxiliary emission controls

P0409 EGR Sensor A Circuit

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modeNo

Exhaust gas recirculation (EGR) routes part of the exhaust back into the intake to lower combustion temperature and NOx. EGR sensor A is usually the valve position sensor (on older Fords the DPFE pressure sensor). P0409 is its general circuit code, for a missing or implausible signal that the module does not classify as low or high. No manufacturer document available to us uses it – GM, Ford and Saab report sensor A as P0405/P0406, Ford intermittent faults as P046D – so the description follows CARB, which requires input circuits to be checked for continuity and range. EGR is usually switched off.

Likely causes

Connector or wire of the position sensor open or loose
EGR valve with integrated sensor faulty
5 V reference or ground disturbed
Engine module

Symptoms

  • Check engine light on
  • EGR switched off
  • Otherwise usually unremarkable

Repair estimate

DifficultyEasyDIY possible
Parts and labour€30–600
Time0.5–2.5 h

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

Parts involved

egr valve position sensoregr valvesensor wiringengine control module

Related codes

P0405P0406P046DP0403

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