P2BA4Catalyst Feedgas Performance
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Needs a drive cycle to confirm a fix
- How the car detects it
- Many diesel SCR systems rely on the oxidation catalyst ahead of them to turn part of the NO into NO2, because a mix near half NO2 lets the SCR reaction run fast at low temperature. P2BA4 reports that this catalyst no longer delivers the needed gas mix. CARB 13 CCR 1968.2 (f)(1.2.3)(B) requires this check for 2015 and later diesels, but lets a maker cover it with the regular NMHC efficiency monitor; Ford's 2023 diesel summary does exactly that via P0420. GM and Cummins patents describe two methods: comparing SCR efficiency measured by the NOx sensors, or judging the catalyst's light-off heat after a hydrocarbon dose. No maker documents P2BA4 publicly. P2BA5 is the same check for a coated particulate filter; the driver mainly notices a lit MIL and possibly SCR codes.
- What you may notice
- Malfunction indicator lamp on
- SCR efficiency codes such as P20EE set as well
- Usually no noticeable change in driving behaviour
- Likely causes
- LikelyOxidation catalyst thermally aged or poisoned (sulphur, oil ash), little NO2 produced
- PossibleCatalyst inlet face coated with soot or unburnt fuel after injector or EGR problems
- PossibleFaulty NOx or exhaust temperature sensor distorting the evaluation
- RareExhaust leak upstream of the catalyst diluting the measured gas
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Hard · Usually a job for a workshop.Typical cost: €300 – €2,500
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.