P0425
Catalyst Temperature Sensor (Bank 1, Sensor 1)
General electrical fault detected in the catalyst temperature sensor on bank 1 sensor position 1. The ECU uses this signal to manage heater control and protect the catalyst from overtemperature.
- Check engine light: Yes
- Emissions related: Yes
- Repair difficulty: medium
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.
- Cat temperature sensor failedCommon
- Wiring or connector faultPossible
Parts involved
- Cat Temperature Sensor
- Sensor Wiring
P0425 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.