Powertrain, generic (extended)

P23E7 EGR C Flow Insufficient Detected

Check engine lightOn

EmissionsRelevant

Drive cycleRequired

Limp modeNo

P23E7 means the module calculates less recirculated exhaust through path C than it expects for the current operating point. The valve may well move correctly; the gas simply does not get through, for example because the passage, cooler or valve seat is choked with soot. GM's 2018 diesel tables illustrate the A-side check P0401: measured air mass is compared with a value expected with EGR active, corrected for barometric pressure, and only at steady speed and fuelling, coolant above 60 °C, outside air above −7 °C and ambient pressure above 74.8 kPa; it is Type B after 350 failures. CARB requires low EGR flow to be detected before NOx exceeds its limits. No manufacturer documents P23E7 publicly. Excess flow is P23E8; valve C stuck closed is P23E6.

Likely causes

Soot-choked EGR passage or valve seat on path C

Clogged EGR cooler in path C

Air mass or pressure sensor reading off, skewing the calculation

Symptoms

Warning lamp after steady cruising
Raised NOx at emissions testing

Repair estimate

DifficultyHardWorkshop job

Parts and labour€100–1,500

Time1–5 h

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

Parts involved

egr valve cegr cooler c

Related codes

P23E8 P23E6 P23E2 P0401 P049B

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