P0428

Symptoms

• Check Engine light is on
• Possible engine power limitation (emergency mode)
• The smell of a burning catalyst (with real overheating)
• Increased fuel consumption
• Possible ringing or knocking noise from under the catalyst if there is real damage

Causes

• Temperature sensor wiring shorted to power
• Faulty catalytic converter temperature sensor
• Real catalyst overheating due to a rich air-fuel mixture
• Misfires (unburned fuel is burned in the catalyst)
• Damaged thermocouple wiring insulation
• ECU malfunction (rare)

How to Fix

1. Read all codes - the presence of misfire or air/fuel mixture codes will indicate the root cause
2. Check the actual temperature sensor readings: do they correspond to the operating temperature?
3. Check the wiring and connector of the sensor for short circuit and integrity
4. Replace the temperature sensor if it is confirmed to be faulty
5. Clear all associated codes (misfire, rich mixture)
6. Allow the catalyst to cool and retest
7. Reset the code and check for reoccurrence

Related codes

Error P0428 by Vehicle Brand