Powertrain, generic · Auxiliary emission controls

P049B EGR B Flow Insufficient 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). P049B means too little flow in circuit B: with the low-pressure valve open the module expects a change in fresh air mass or manifold pressure, or a modelled EGR volume, and the actual flow stays below the threshold. FCA documents it on the 3.0-litre EcoDiesel third generation in the 2020 Ram 1500, partly as a false trigger fixed by a software update; thresholds are not published.

Likely causes

Software or calibration (false trigger)
Low-pressure EGR valve sooted or stuck closed
Low-pressure EGR cooler or line blocked
Implausible sensors (air mass, pressure difference)

Symptoms

  • Check engine light on
  • Sluggish acceleration (FCA bulletin)
  • Higher NOx

Repair estimate

DifficultyHardWorkshop job
Parts and labour€100–1,500
Time0.5–5 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

P049CP049AP0401P045FP045EP049E

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