P0042
HO2S Heater Control Circuit Bank 1 Sensor 3
Generic electrical fault in the heater control of the bank 1, sensor 3 oxygen sensor (typically a third sensor downstream of multi-stage cat or NOx trap).
- Check engine light: Yes
- Emissions related: Yes
- Repair difficulty: medium
Common causes
Ordered by how often each turns out to be the cause.
- Heater element openCommon
- Heater wiring or connector faultPossible
Parts involved
- Oxygen Sensor B1s3 Heater
- Heater Wiring
P0042 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.