P0434
Heated Catalyst Temperature Below Threshold (Bank 2)
- Severity
- Medium
- Driving
- Drivable — book it in
The heated catalyst on bank 2 is not reaching the temperature it needs. A converter only works above a certain temperature, and this one has an electric heater specifically to get it there quickly - so this code usually points at the heater or its supply rather than at the converter itself.
Possible causes
- CommonFailed catalyst heater element
- CommonBlown fuse or failed relay on the heater circuit
- CommonCorroded high-current connections at the heater
- CommonFaulty catalyst temperature sensor
- PossibleWiring damage
- PossibleExhaust leak cooling the converter
What you might notice
- Check engine light on
- Failed emissions test
- Slight loss of power
- Sulphurous or rotten-egg smell from the exhaust
- Rattling from the converter if its internals have broken up
- Often no symptom the driver notices
What to check, in order
- Check the fuse and relay for the heater circuit - these carry heavy current and their connections suffer for it.
- Watch the catalyst temperature on the live data screen from a cold start. It should climb well ahead of the surrounding exhaust.
- Check for exhaust leaks upstream, which cool the converter and stop it lighting off.
- Measure the heater element resistance against specification.
- Establish whether the temperature sensor is reading correctly before condemning the heater.
Read this code from your own car
Plug an ELM327 adapter into the OBD-II port under the dashboard. Pin16 reads every stored, pending and permanent code, explains each one like this page does — offline, with no account — and shows what the car recorded when the fault was set.
Where this code sits
P00xxP01xxP02xxP03xxP04xxP05xxP06xxP07xxP08xxP09xxP0AxxP0BxxP0CxxP0DxxP0ExxP0FxxP10xxP11xxP12xxP13xxP14xxP15xxP16xxP17xxP18xxP19xxP1AxxP1BxxP1CxxP1DxxP1ExxP1FxxP20xxP21xxP22xxP23xxP24xxP25xxP26xxP27xxP28xxP29xxP2AxxP2BxxP2CxxP2DxxP2ExxP2FxxP30xxP31xxP32xxP33xxP34xxP35xxP36xxP37xxP38xxP39xxP3AxxP3BxxP3CxxP3DxxP3ExxP3Fxx
Auxiliary emission controls
P0400P0401P0402P0403P0404P0405P0406P0407P0408P0409P0410P0411P0412P0413P0414P0415P0416P0417P0418P0419P0420P0421P0422P0423P0424P0425P0426P0427P0428P0429P0430P0431P0432P0433P0434P0435P0436P0437P0438P0439P0440P0441P0442P0443P0444P0445P0446P0447P0448P0449P0450P0451P0452P0453P0454P0455P0456P0457P0458P0459P0460P0461P0462P0463P0464P0465P0466P0467P0468P0469P0470P0471P0472P0473P0474P0475P0476P0477P0478P0479P0480P0481P0482P0483P0484P0485P0486P0487P0488P0489P0490P0491P0492P0493P0494P0495P0496P0497P0498P0499