P04FE
Catalyst Heater Circuit Performance Bank 1
The catalyst heater on bank 1 is electrically intact but does not deliver the expected thermal effect - measured catalyst light-off time is longer than calibrated. Heater element ageing, increased contact resistance, or a partial winding failure are typical causes.
- Check engine light: Yes
- Emissions related: Yes
- Repair difficulty: hard
Symptoms
- Check engine light on
- Failed emissions inspection
- Possibly slightly increased fuel consumption
- Sulfur (rotten egg) smell from exhaust under load
Common causes
Ordered by how often each turns out to be the cause.
- Heater element aged - reduced power outputCommon
- Increased contact resistance in supplyPossible
Parts involved
- Electric Catalyst Heater B1
P04FE is a generic OBD-II code defined by SAE J2012. Exact wording and diagnostic procedure vary by manufacturer and model. Code definitions are drawn from the public-domain OBDex dataset; the workshop notes are our own.