P042A
Catalyst Temperature Sensor Circuit (Bank 1 Sensor 2)
A general electrical fault on the catalyst temperature sensor at bank 1 sensor 2.
- 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.
- Sensor failedCommon
Parts involved
- Exhaust Temperature Sensor
P042A 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.