OBD-II Generic Error Code P0428: How to Fix It

Medium 1-2 hours Medium Severity Verified June 2026
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Error Code
P0428
Brand
OBD-II Generic
Product Type
automotive
Severity
Medium
DIY Difficulty
Medium
Estimated Fix Time
1-2 hours
Error code P0428 means the catalytic converter temperature sensor on Bank 1 is reporting a voltage higher than expected. This indicates the catalyst may be overheating, potentially due to an overly rich fuel mixture, misfiring, or a faulty sensor. Driving with this code can damage the catalytic converter, so it should be addressed promptly.
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Tools You'll Need

How to Fix Error Code P0428

  1. Scan and Record Freeze Frame Data

  2. Inspect Exhaust System for Leaks

    Let the engine cool down before touching exhaust components to avoid burns.

  3. Check Catalyst Temperature Sensor Wiring

  4. Test the Temperature Sensor

  5. Check for Engine Misfires or Rich Condition

  6. Inspect Catalytic Converter for Damage

    Catalytic converter replacement requires cutting and welding; consider professional help.

Parts You May Need

Catalyst temperature sensor
Check Price on Amazon
Oxygen sensor (if upstream)
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Catalyst temperature sensor
Check Price on Amazon
Oxygen sensor (if upstream)
Check Price on Amazon
Catalyst temperature sensor
Check Price on Amazon
Oxygen sensor (if upstream)
Check Price on Amazon
Catalyst temperature sensor
Check Price on Amazon
Oxygen sensor (if upstream)
Check Price on Amazon
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When to Call a Professional

If you are not comfortable working with exhaust systems or electrical diagnostics, or if the catalytic converter needs replacement (requires welding), consult a professional mechanic.

Frequently Asked Questions

Can I drive with error code P0428?
It is not recommended to drive long distances with P0428, as the catalytic converter may overheat and become damaged, leading to costly repairs. Have the issue diagnosed as soon as possible.
Will a bad oxygen sensor cause P0428?
Yes, a faulty oxygen sensor (upstream) can cause the engine to run rich, leading to catalyst overheating and triggering P0428. Check for related codes like P0420 or P0135.
How much does it cost to fix P0428?
Costs vary: a temperature sensor replacement can be $100-$200, while catalytic converter replacement can be $500-$2000 or more. Diagnosis costs around $100-$150.
What does 'Catalyst temp sensor high B1' mean?
It means the temperature sensor on Bank 1 (engine side with cylinder #1) is reporting a voltage higher than normal, indicating the catalytic converter is overheating.
Can I replace just the temperature sensor instead of the catalytic converter?
Yes, if the converter is not damaged. However, if the overheating is due to a bad converter, replacing only the sensor will not fix the root cause and the code will return.

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