P0434Heated Catalyst Temperature Below Threshold 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. P0434 implements CARB's heated-catalyst rule for bank 2 (the side without cylinder 1): the catalyst must reach its intended temperature within a time set by the manufacturer after the start, measured by a temperature sensor or modelled from heating power. If it does not, the heater is too weak – supply voltage, contact resistance, an ageing element – or heat losses are too high. An open heater circuit is reported as P0429/P0439 instead. 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
- PossibleHeating element aged or partly faulty
- PossibleSupply too weak (battery, 48 V system, relay, contact resistance)
- PossibleCatalyst temperature sensor reads wrong
- RareEngine module or calibration
- 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.