P0420 on HYUNDAI TUCSON — Catalyst System Efficiency Below Threshold Bank 1

Q: "What does P0420 mean on a HYUNDAI TUCSON?"

"P0420 indicates: Catalyst System Efficiency Below Threshold Bank 1. This is a emission controls code. 12 HYUNDAI TUCSON owners have reported this to NHTSA."

Q: "What are the most common causes of P0420 on HYUNDAI TUCSON?"

"Based on 12 NHTSA reports, the most commonly cited components are: Engine, Power Train,Engine, Engine And Engine Cooling. These percentages are based on the component field in owner complaints."

Q: "Is P0420 a safety concern on HYUNDAI TUCSON?"

"Of 12 NHTSA reports for P0420 on HYUNDAI TUCSON, 1 involved a fire. Always consult a qualified mechanic for any diagnostic trouble code."

Q: "What should I do if my HYUNDAI TUCSON 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 HYUNDAI TUCSON

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.

12 HYUNDAI TUCSON owners have reported this issue to NHTSA across model years 2005-2020. Most reports come from the 2019, 2016 model years. The most commonly reported component is Engine (41.7% of reports).

Real HYUNDAI TUCSON Owner Reports

Source: NHTSA Complaints Database

"Initial issues on vehicle presented in january 2021 with various check engine light codes including p0133. although vehicle passed emissions in 2020, various check engine codes for mass air flow sensor, oxygen sensors, misfire for various cylinders."

— 2005 HYUNDAI TUCSON owner · POWER TRAIN,ENGINE · Filed 05/08/2021

"On [XXX], I purchased a 2016 Hyundai Tucson Sport, at the Landover-Jaguar South Hills dealer in Canonsburg, PA. On [XXX] the “check engine” light came on. Since I was 2 hours from home, I purchased a code reader to assess the issue. It read “A P0420 code”."

— 2016 HYUNDAI TUCSON owner · ENGINE · Filed 11/03/2024

"Hyundai dealership just gave me my vehicle back after having it for 3 months replacing the engine due to engine failure which a class action law suite was filed about."

— 2016 HYUNDAI TUCSON owner · POWER TRAIN,ENGINE · Filed 05/14/2022

"My 2017 Hyundai Tucson 1.6 liter is experiencing severe engine issues that closely mirror those subject to recent class action lawsuits. The engine exhibits excessive oil consumption. I have experienced a sudden loss of power on roadways in traffic as well as on the highway."

— 2017 HYUNDAI TUCSON owner · ENGINE · Filed 07/14/2025

"The contact owns a 2019 Hyundai Tucson. The contact stated that the vehicle had been experiencing excessive oil consumption, and the check engine warning light was intermittently illuminated. The contact stated that while driving 25-30 MPH, the vehicle was shuddering."

— 2019 HYUNDAI TUCSON owner · ENGINE AND ENGINE COOLING · Filed 03/25/2025

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

📊 Complaint Trend by Model Year

1

'05

2

'16

1

'17

6

'19

2

'20

Common Causes on HYUNDAI TUCSON

Based on NHTSA complaint component analysis for this vehicle.

ENGINE 41.7%

POWER TRAIN,ENGINE 25%

ENGINE and ENGINE COOLING 8.3%

UNKNOWN or OTHER,FUEL/PROPULSION SYSTEM 8.3%

POWER TRAIN 8.3%

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 HYUNDAI TUCSON? ▾

P0420 indicates: Catalyst System Efficiency Below Threshold Bank 1. This is a emission controls code. 12 HYUNDAI TUCSON owners have reported this to NHTSA.

What are the most common causes of P0420 on HYUNDAI TUCSON? ▾

Based on 12 NHTSA reports, the most commonly cited components are: Engine, Power Train,Engine, Engine And Engine Cooling. These percentages are based on the component field in owner complaints.

Is P0420 a safety concern on HYUNDAI TUCSON? ▾

Of 12 NHTSA reports for P0420 on HYUNDAI TUCSON, 1 involved a fire. Always consult a qualified mechanic for any diagnostic trouble code.

What should I do if my HYUNDAI TUCSON 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.