P0420 on KIA FORTE — Catalyst System Efficiency Below Threshold Bank 1

Q: "What does P0420 mean on a KIA FORTE?"

"P0420 indicates: Catalyst System Efficiency Below Threshold Bank 1. This is a emission controls code. 2 KIA FORTE owners have reported this to NHTSA."

Q: "What are the most common causes of P0420 on KIA FORTE?"

"Based on 2 NHTSA reports, the most commonly cited components are: Engine, Engine,Fuel/Propulsion System. These percentages are based on the component field in owner complaints."

Q: "Is P0420 a safety concern on KIA FORTE?"

"Of 2 NHTSA reports for P0420 on KIA FORTE, 1 involved a crash. Always consult a qualified mechanic for any diagnostic trouble code."

Q: "What should I do if my KIA FORTE shows P0420?"

"1) Check for recalls on your VIN at nhtsa.gov/recalls. 2) Get a professional diagnosis — a code alone doesn't identify the exact failed part. 3) Get 2-3 repair estimates to compare."

What P0420 Means on Your KIA FORTE

P0420 is a diagnostic trouble code indicating: Catalyst System Efficiency Below Threshold Bank 1. This code relates to the emission controls system. The vehicle's computer detected a condition outside normal operating parameters and stored this code.

2 KIA FORTE owners have reported this issue to NHTSA across model years 2017-2020. Most reports come from the 2017, 2020 model years. The most commonly reported component is Engine (50.0% of reports).

Real KIA FORTE Owner Reports

Source: NHTSA Complaints Database

"Repeated engine failure. 10/1/2022 "internal problem required engine teardown found exhaust cvvt dowel pin had sheared off inside of exhaust camshaft causing excessive play. Replaced exhaust cvvt exhaust camshaft valve cover gasket rtv exhaust cvvt bolt timing chain tensioner timing chain and ocv."

— 2017 KIA FORTE owner · ENGINE · Filed 10/01/2022 ⚠️ Crash reported

"I own a 2020 Kia Forte LXS with approximately 136,000 miles. The check engine light came on with code P0420 (“catalyst system efficiency below threshold”), and an Express Oil Change & Tire Engineers location confirmed the catalytic converter is failing."

— 2020 KIA FORTE owner · ENGINE,FUEL/PROPULSION SYSTEM · Filed 08/11/2025

All reports filed by vehicle owners directly with the U.S. Department of Transportation.

📊 Complaint Trend by Model Year

1

'17

1

'20

Common Causes on KIA FORTE

Based on NHTSA complaint component analysis for this vehicle.

ENGINE 50%

ENGINE,FUEL/PROPULSION SYSTEM 50%

What To Do Next

1
Check for recalls on YOUR VIN
Go to nhtsa.gov/recalls and enter your VIN. If your vehicle is covered, repairs are free.
2
Get a proper diagnosis
A code alone doesn't tell you the exact failed part. A diagnostic at a shop ($50–$150) pinpoints the root cause before you spend money on parts.
3
Compare repair quotes
Get 2–3 quotes. Dealer vs. independent shop prices often differ 30–50% for the same repair.

Frequently Asked Questions

What does P0420 mean on a KIA FORTE? ▾

P0420 indicates: Catalyst System Efficiency Below Threshold Bank 1. This is a emission controls code. 2 KIA FORTE owners have reported this to NHTSA.

What are the most common causes of P0420 on KIA FORTE? ▾

Based on 2 NHTSA reports, the most commonly cited components are: Engine, Engine,Fuel/Propulsion System. These percentages are based on the component field in owner complaints.

Is P0420 a safety concern on KIA FORTE? ▾

Of 2 NHTSA reports for P0420 on KIA FORTE, 1 involved a crash. Always consult a qualified mechanic for any diagnostic trouble code.

What should I do if my KIA FORTE shows P0420? ▾

1) Check for recalls on your VIN at nhtsa.gov/recalls. 2) Get a professional diagnosis — a code alone doesn't identify the exact failed part. 3) Get 2-3 repair estimates to compare.