OBD-II FAULT CODE
P0428
Catalyst Temperature Sensor High Input (Bank 1)
Meaning, symptoms, likely causes, diagnostic checks and repair guidance for P0428.
- Check Engine light
- Poor drivability or reduced fuel economy depending on fault
- Possible loss of power if catalyst is restricted
- Aged catalytic converter
- Exhaust leak
- O2 sensor issue
- Misfire or rich running damaging catalyst
- High signal voltage
- Scan all modules and record freeze-frame data before clearing codes
- Check battery voltage and related fuses
- Check for misfires/fuel trim issues first
- Inspect exhaust leaks and compare upstream/downstream O2 sensor activity
- Check sensor ground and signal circuit for short to voltage
- Fix engine running faults or exhaust leaks before replacing catalyst
- Replace catalyst only after confirming it failed
- Repair ground/signal circuit or replace confirmed faulty sensor
Related Codes
Need more help?
Search manuals, wiring diagrams and technical service bulletins.
Not sure what to do next?
Get step-by-step instructions and professional repair information.
Disclaimer: Information is provided for general guidance only and may not apply to all vehicles. Always consult a qualified technician.