Powertrain, generic · Auxiliary emission controls

P046C EGR Sensor A Circuit Range/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. Which part EGR sensors A and B are depends on the maker: sensor A is usually the position sensor of EGR valve A; GM's Duramax diesels of 2017/18 use sensor B for the coolant temperature sensor at the inlet of the high-pressure EGR cooler, FCA for the position sensor of the low-pressure valve. P046C means the signal of sensor A is electrically valid but implausible. GM's diesels (6.6-litre Duramax LML and others from 2014) set it when the actual valve position deviates from the target by 5 % or more for 8 s, with offset learning completed and at least 11 V (MIL after two trips). Ford uses P0405/P0406/P046D for sensor A instead. EGR is then switched off or limited.

Likely causes

EGR valve coked and stiff, actual position does not follow
Position sensor worn or offset shifted
Contact resistance at connector or 5 V supply
Values not relearned after valve replacement

Symptoms

  • Check engine light on
  • EGR switched off, possibly higher NOx
  • Rarely jerking or lack of power

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€150–900
Time1–3 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

P046DP0405P0406P0409P0404

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