P0439Catalyst Heater Control Circuit/Open 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 a support catalyst so that it works soon after a cold start (Emitec EMICAT, 12–48 V); it was tried on Californian petrol cars in the 1990s and is used today mainly on diesels, for example Audi's 3.0 TDI from 2014 and 48-volt diesel vans. P0439 is the electrical check of the catalyst heater of bank 2 (the side without cylinder 1): the module drives it via a relay or power stage and detects an open control circuit or heating element from the driver feedback, as CARB requires for output circuits. The heater then fails, the catalyst lights off later and P0424/P0434 may follow; the engine itself runs normally. No manufacturer document available to us uses this code.
- What you may notice
- Check engine light on
- Higher emissions after a cold start
- Otherwise usually unremarkable
- Likely causes
- LikelyWire or connector to the heating element open (heat, corrosion)
- PossibleHeating element burnt out
- PossibleRelay, fuse or power stage faulty
- RareEngine module
- 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 – €2,500
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.