P0420 on CHEVROLET TRAVERSE — Catalyst System Efficiency Below Threshold Bank 1

Q: "What does P0420 mean on a CHEVROLET TRAVERSE?"

"P0420 indicates: Catalyst System Efficiency Below Threshold Bank 1. This is a emission controls code. 8 CHEVROLET TRAVERSE owners have reported this to NHTSA."

Q: "What are the most common causes of P0420 on CHEVROLET TRAVERSE?"

"Based on 8 NHTSA reports, the most commonly cited components are: Engine, Unknown Or Other, Engine And Engine Cooling,Engine. These percentages are based on the component field in owner complaints."

Q: "Is P0420 serious on my CHEVROLET TRAVERSE?"

"Of 8 NHTSA reports for this code on CHEVROLET TRAVERSE, none involved a crash or fire. However, any diagnostic code should be evaluated by a qualified mechanic."

Q: "What should I do if my CHEVROLET TRAVERSE 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 CHEVROLET TRAVERSE

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.

8 CHEVROLET TRAVERSE owners have reported this issue to NHTSA across model years 2010-2020. Most reports come from the 2020, 2010 model years. The most commonly reported component is Engine (50.0% of reports).

Real CHEVROLET TRAVERSE Owner Reports

Source: NHTSA Complaints Database

"Recently bought this traverse 2010 ltz from a private owner after 200 miles on the road the check engine light triggered a few codes p0008-p0017-p0420, upon extensive diagnostics at four different places."

— 2010 CHEVROLET TRAVERSE owner · ENGINE · Filed 06/04/2020

"My vehicle was getting a check engine code #P0420, took to my GM dealer for service on [XXX]. RK Chevrolet in Virginia Beach, VA. Was told the error was caused by the mounting bracket on the front exhaust pipe had separated from the pipe, resulting in a hole in the pipe."

— 2018 CHEVROLET TRAVERSE owner · ENGINE · Filed 01/26/2024

"2019 chevy traverse check engine light came on then went off for a couple of weeks. The engine light came back on and I took it in to dealership. They found code p0420 which is fail code catalytic converter."

— 2019 CHEVROLET TRAVERSE owner · UNKNOWN OR OTHER · Filed 12/05/2022

"The contact owns a 2020 Chevrolet Traverse. The contact stated while driving 45 MPH, the vehicle jerked, with an abnormal sound coming from underneath the vehicle. In addition, the contact stated the vehicle failed to accelerate as intended while depressing the accelerator pedal."

— 2020 CHEVROLET TRAVERSE owner · ENGINE AND ENGINE COOLING,ENGINE · Filed 05/12/2025

"Engine light came on couple weeks ago. Code is p0420 so I did some research and inspected the exhaust system and found the weld on the support bracket of the exhaust pipes was cracked and wore a hole between the pipe and the bracket."

— 2020 CHEVROLET TRAVERSE owner · ENGINE · Filed 06/09/2025

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

📊 Complaint Trend by Model Year

1

'10

1

'18

1

'19

5

'20

Common Causes on CHEVROLET TRAVERSE

Based on NHTSA complaint component analysis for this vehicle.

ENGINE 50%

UNKNOWN or OTHER 25%

ENGINE and ENGINE COOLING,ENGINE 12.5%

POWER TRAIN 12.5%

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 CHEVROLET TRAVERSE? ▾

P0420 indicates: Catalyst System Efficiency Below Threshold Bank 1. This is a emission controls code. 8 CHEVROLET TRAVERSE owners have reported this to NHTSA.

What are the most common causes of P0420 on CHEVROLET TRAVERSE? ▾

Based on 8 NHTSA reports, the most commonly cited components are: Engine, Unknown Or Other, Engine And Engine Cooling,Engine. These percentages are based on the component field in owner complaints.

Is P0420 serious on my CHEVROLET TRAVERSE? ▾

Of 8 NHTSA reports for this code on CHEVROLET TRAVERSE, none involved a crash or fire. However, any diagnostic code should be evaluated by a qualified mechanic.

What should I do if my CHEVROLET TRAVERSE 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.