P1031low severityPowertrain
HO2S Heater Current Monitor Control Circuit Bank 1
on 2002 Cadillac Escalade 6.0L V8 · 4WD
What this code means
The PCM detected a fault in the heated oxygen sensor heater current monitor control circuit for Bank 1 Sensor 1. The heater is used to bring the O2 sensor up to operating temperature quickly.
Symptoms
- Check Engine Light
- Poor cold-start fuel economy
- Extended warmup emissions
- Failed emissions test
Common causes
- Faulty O2 sensor heater element
- Blown heater circuit fuse
- Corroded wiring or connector
- PCM heater driver failure
Diagnostic steps
- Check O2 sensor heater fuse
- Test heater circuit resistance
- Inspect wiring and connectors
- Test PCM heater output
Repair notes
Replace O2 sensor if heater resistance is out of spec. Check fuse and wiring first.
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