P0428 - Catalyst Temperature Sensor High Input (Bank 1 Sensor 1)

The catalyst temperature sensor signal on bank 1 sensor 1 is higher than expected.

Code Overview

The catalyst temperature sensor signal on bank 1 sensor 1 is higher than expected.

Common Causes

• Aging catalyst
• Exhaust leak ahead of the catalyst or sensor
• Sensor or wiring fault
• Upstream fueling or misfire problem

Diagnostic Steps

1. Fix any active misfire or fueling codes first
2. Check for exhaust leaks ahead of the converter
3. Compare sensor data before replacing catalyst parts

Likely Repairs & Cost Guides

Use test results to confirm the fault before pricing the repair.

Related OBD Codes

Browse the closest code-family pages when the same fault pattern often shows up nearby.

Next Steps

Move from the code to a diagnosis path, then into repair pricing once the fault is confirmed.