Powertrain, generic · Auxiliary emission controls

P046F EGR Sensor B Circuit Intermittent/Erratic

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. 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. P046F means jumps or dropouts of sensor B. GM's Duramax diesels set it when the value leaves a narrowing window around the last valid reading – 40 of 50 samples of 100 ms, MIL after two trips. A substitute value is then used and EGR cooler monitoring is suspended. Usually a loose contact or broken wire is the cause.

Likely causes

Loose contact at the sensor connector
Chafed wire or vibration break
Sensor faulty internally
Engine module

Symptoms

  • Check engine light on, may come and go
  • Usually no change in driving

Repair estimate

DifficultyEasyDIY possible
Parts and labour€30–300
Time0.3–1.5 h

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

Parts involved

egr sensor bsensor wiringengine control module

Related codes

P046EP0407P0408P046DP044E

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