P04F9Catalyst Heater Circuit Intermittent Bank 2
- 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
- An electrically heated catalyst has a heating disc ahead of the catalyst so that it works soon after a cold start; Emitec's EMICAT runs on 12, 24 or 48 V and draws up to about 300 A. It is in series production on 48-volt mild-hybrid diesel vans since 2022. P04F9 concerns the heated catalyst of bank 2 – no production vehicle with two heated catalysts is known. The code means the heater circuit shows brief or repeated circuit faults that do not persist – typically a loose contact at the high-current connectors or a wire broken by vibration and heat. No manufacturer document available to us uses this code – Ford, for example, states that heated catalyst monitoring is not supported – so thresholds and warning-lamp logic are not documented; the description follows CARB and patents for the same part.
- What you may notice
- Check engine light on (depending on the maker)
- Higher emissions after a cold start
- Otherwise usually unremarkable
- Likely causes
- LikelyLoose contact at the heater or module connector
- PossibleWire broken near the exhaust
- PossibleCorrosion at ground or connector
- RareInternal contact point of the heating disc
- 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: €50 – €800
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.