P23E8EGR C Flow Excessive Detected
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- Needs a drive cycle to confirm a fix
- How the car detects it
- P23E8 reports that more exhaust gas passes through the third recirculation path, C, than the module allows for the current operating point – the reverse of P23E7. A valve C that does not seat fully, a leaking bypass or a flow sensor reading too high are the usual explanations. CARB requires the OBD system to recognise EGR flow so high that the system can no longer bring it down to the commanded rate. No manufacturer documents P23E8 publicly. GM's 2011 6.6 L LGH diesel shows the equivalent logic for path A (P0402): actual and desired air mass are compared, and a controller deviation between 0.4 and 1.2 g per revolution between 1150 and 1600 rpm, held for 8 s, sets a Type B fault. Expect rough idle, stalling, misfire or smoke.
- What you may notice
- Rough or unstable idle
- Engine stalls when coming to a stop
- Hesitation or misfire under load
- Visible smoke on diesel engines
- Likely causes
- LikelyEGR valve C held partly open by carbon deposits
- PossibleWorn valve seat or leaking bypass in path C
- PossibleAir-mass or EGR flow sensor reading off, so flow is overestimated
- RareControl software needing an update
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Medium · Usually a job for a workshop.Typical cost: €100 – €1,200
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.