Powertrain, generic (extended)

P23E5 EGR C Control Stuck Open

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modePossible

P23E5 means EGR valve C stays open although it is commanded closed. The 2018 GM diesel calibration decides the A-side code P042E like this: once the driver is switched off, the return spring should bring the valve to its closed default within 2 s; if the measured position is still above 5 % after that, the code sets at once as Type A, MIL on the first trip. Comparable logic would suit valve C. Too much exhaust gas at idle or under load causes rough running, misfire, stalling and, on diesels, smoke, which is why such faults are rated urgently. Carbon build-up holding the flap open is the usual cause; a broken spring or jammed linkage are others. No manufacturer documents P23E5 publicly. Stuck closed: P23E6, excessive flow: P23E8.

Likely causes

Carbon deposits holding valve C open
Broken return spring in valve C
Jammed shaft or linkage

Symptoms

  • Rough idle or stalling
  • Misfire and lack of power
  • Smoke on diesel engines
  • Warning lamp on the first trip

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€100–1,200
Time0.5–4 h

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

Parts involved

egr valve c

Related codes

P23E6P23E8P23E2P042EP045E

References: gsi.ext.gm.com, en.wikipedia.org, law.cornell.edu.