OBD-II FAULT CODE
P0426
Catalyst Temperature Sensor Range/Performance (Bank 1)
Meaning, symptoms, likely causes, diagnostic checks and repair guidance for P0426.
- 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
- Signal out of expected range
- 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
- Compare live data to expected value and inspect mechanical operation
- Fix engine running faults or exhaust leaks before replacing catalyst
- Replace catalyst only after confirming it failed
- Repair mechanical cause, clean/replace sticking actuator, or replace sensor after confirmation
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Disclaimer: Information is provided for general guidance only and may not apply to all vehicles. Always consult a qualified technician.