P0421
Catalyst 1 Efficiency Below Threshold Bank 1
P0421 is an OBD-II diagnostic trouble code meaning: Catalyst 1 Efficiency Below Threshold Bank 1. Common causes: faulty catalytic converter, damaged or dirty oxygen sensors. Estimated repair cost: $167–556.
Symptoms
- Check Engine light comes on
- Reduced engine power
- Increased fuel consumption
- Unusual odor from the exhaust system
Causes
- Faulty catalytic converter
- Damaged or dirty oxygen sensors
- Leaks in the exhaust system
- Misfires
- Use of low-quality fuel
How to Fix
- Check the condition of the oxygen sensors
- Inspect the exhaust system for leaks
- Check the catalytic converter for blockage or damage.
- Replace the catalytic converter if necessary
- Reset the error and check if it returns
Related codes
Error P0421 by Vehicle Brand
FAQ
What does the P0421 code mean?
P0421 is an OBD-II diagnostic trouble code that indicates: Catalyst 1 Efficiency Below Threshold Bank 1
What causes a P0421 error code?
The most common causes of P0421 include: Faulty catalytic converter; Damaged or dirty oxygen sensors; Leaks in the exhaust system; Misfires.
How do I fix a P0421 diagnostic trouble code?
To fix P0421: Check the condition of the oxygen sensors. Inspect the exhaust system for leaks. Check the catalytic converter for blockage or damage.. For a complete diagnosis, use an OBD-II scanner.
Is it safe to drive with P0421?
Limited driving only, diagnose soon
How much does it cost to fix P0421?
The estimated repair cost for P0421 is $167–556. Actual cost depends on your vehicle, location, and labor rates.
See also: Russian version · NationStat