Powertrain, generic · Auxiliary emission controls

P049A EGR B Flow

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). P049A is the general flow fault of circuit B, used where the module does not separate too little from too much; CARB requires low and high flow to be detected, mostly by comparing air mass, manifold pressure or lambda with a model. No manufacturer document available to us uses P049A – GM has only position and actuator codes for its low-pressure EGR, FCA uses P049B. Low-pressure EGR is then switched off.

Likely causes

Low-pressure EGR valve sooted or sticking

Low-pressure EGR cooler or line blocked or leaking

Flap creating the pressure difference faulty

Sensors (air mass, pressure difference, position sensor B) implausible

Symptoms

Check engine light on
EGR switched off, usually no noticeable change
Higher NOx

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 valvelow pressure egr cooleregr b circuitengine control module

Related codes

P049B P049C P0400 P045A P049E

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