Powertrain, generic · Auxiliary emission controls

P049C EGR B Flow Excessive Detected

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. Circuit B is the second EGR path; on diesels with two circuits it is the low-pressure EGR, which takes exhaust after the particulate filter and feeds it in before the turbo compressor (GM diesels 2016–18, FCA's 2.2 and 3.0 diesels). P049C means too much flow in circuit B – fresh air mass drops further than modelled, or EGR flows with the low-pressure valve closed; CARB explicitly requires a leaking valve to be detected. No manufacturer document available to us uses P049C; the closest is FCA's P045E for a low-pressure valve stuck open. Smoke, lack of power and rough idle follow, and low-pressure EGR is switched off.

Likely causes

Low-pressure EGR valve stuck open or not sealing (soot)
Position sensor B implausible (valve seemingly closed)
Leak between exhaust side and intake
Air mass meter reading too low

Symptoms

  • Check engine light on
  • Lack of power, black smoke
  • Rough idle or misfire, in extreme cases stalling

Repair estimate

DifficultyHardWorkshop job
Parts and labour€150–1,500
Time1–5 h

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

Parts involved

low pressure egr valveegr b circuitmaf sensorengine control module

Related codes

P049BP049AP0402P045EP0407

References: law.cornell.edu, patents.google.com, static.nhtsa.gov.