Honda Accord
P0421
The P0421 code indicates "Warm Up Catalyst Efficiency Below Threshold (Bank 1)" in a 10th generation Honda Accord (2018-2022). This issue typically suggests a malfunction in the catalytic converter or its related components.
2 SolutionsP-CodePowertrain
P
Error Code Type
Powertrain
Components
1 affected
Exhaust System
Symptoms
7 common
- •Check engine light illuminated
- •Decreased fuel efficiency
- •Unusual exhaust smells (e.g., sulfur or rotten egg odor)
- +4 more
Most Affected Generations
2 generations
CP/CS
1
11th Gen
1
Top Affected Components
1 component
Exhaust System
2
Severity Levels
1 level
high
2
Quick Facts
2
Total Solutions
1
Affected Components
7
Common Symptoms
2
Generations
All Solutions
Showing 2 of 2 solutions for error code P0421 across all generations.