P0420 on SUBARU OUTBACK — Catalyst System Efficiency Below Threshold Bank 1

Q: "What does P0420 mean on a SUBARU OUTBACK?"

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

Q: "What are the most common causes of P0420 on SUBARU OUTBACK?"

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

Q: "Is P0420 serious on my SUBARU OUTBACK?"

"Of 2 NHTSA reports for this code on SUBARU OUTBACK, none involved a crash or fire. However, any diagnostic code should be evaluated by a qualified mechanic."

Q: "What should I do if my SUBARU OUTBACK 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 SUBARU OUTBACK

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 SUBARU OUTBACK owners have reported this issue to NHTSA across model years 2011-2012. Most reports come from the 2011, 2012 model years. The most commonly reported component is Fuel/Propulsion System (50.0% of reports).

Real SUBARU OUTBACK Owner Reports

Source: NHTSA Complaints Database

"P0420 code o2 sensors. i had this problem back in 2017. cruise, skid control, brake light and check engine light come on. subaru said it was the catalytic converter, 02 sensors and associated piping. subaru replaced it for free in 2017."

— 2011 SUBARU OUTBACK owner · FUEL/PROPULSION SYSTEM · Filed 08/02/2019

"The contact's girlfriend owns a 2012 Subaru Outback. The contact stated that the vehicle hesitated while starting. In addition, the contact attempted to jumpstart the vehicle; however, the vehicle failed to start. The check engine warning light was intermittently illuminated."

— 2012 SUBARU OUTBACK owner · ENGINE AND ENGINE COOLING,ELECTRICAL SYSTEM,AIR BAGS · Filed 06/15/2019

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

📊 Complaint Trend by Model Year

1

'11

1

'12

Common Causes on SUBARU OUTBACK

Based on NHTSA complaint component analysis for this vehicle.

FUEL/PROPULSION SYSTEM 50%

ENGINE and ENGINE COOLING,ELECTRICAL SYSTEM,AIR BAGS 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 SUBARU OUTBACK? ▾

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

What are the most common causes of P0420 on SUBARU OUTBACK? ▾

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

Is P0420 serious on my SUBARU OUTBACK? ▾

Of 2 NHTSA reports for this code on SUBARU OUTBACK, none involved a crash or fire. However, any diagnostic code should be evaluated by a qualified mechanic.

What should I do if my SUBARU OUTBACK 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.