P20F1SCR NOx Pre-Catalyst Over Temperature (Bank 2)
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- How the car detects it
- P20F1 reports an over-temperature of the SCR pre-catalyst on bank 2, the close-coupled front stage of a two-stage system in the second exhaust line. Both conditions must be met for the code to exist on a vehicle: separate aftertreatment per bank and a split SCR with a front brick near the turbocharger outlet. No manufacturer documents this combination publicly. Paccar's patent US11976582 shows why a front stage in that position is exposed to the hottest exhaust and to regeneration heat, and 40 CFR 1036.115 obliges heavy-duty engine makers to protect vanadium-based catalysts against temperatures that cause sublimation. Compared with P20F0, which covers the main bank 2 catalyst, the front stage heats up faster and reacts first to fuel slip from bank 2 cylinders. Lasting damage would show up as P20F3.
- What you may notice
- Malfunction indicator lamp on
- Front-stage dosing or regeneration suspended
- Likely causes
- LikelyFuel slip from bank 2 cylinders (injector leak, misfire, post-injection fault)
- PossiblePre-catalyst temperature sensor on bank 2 reading too high
- PossibleRegeneration heat reaching the front stage
- 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: €100 – €2,500
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.