P0420 on NISSAN ALTIMA — Catalyst System Efficiency Below Threshold Bank 1

Q: "What does P0420 mean on a NISSAN ALTIMA?"

"P0420 indicates: Catalyst System Efficiency Below Threshold Bank 1. This is a emission controls code. 3 NISSAN ALTIMA owners have reported this to NHTSA."

Q: "What are the most common causes of P0420 on NISSAN ALTIMA?"

"Based on 3 NHTSA reports, the most commonly cited components are: Engine And Engine Cooling, Electrical System. These percentages are based on the component field in owner complaints."

Q: "Is P0420 serious on my NISSAN ALTIMA?"

"Of 3 NHTSA reports for this code on NISSAN ALTIMA, none involved a crash or fire. However, any diagnostic code should be evaluated by a qualified mechanic."

Q: "What should I do if my NISSAN ALTIMA 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 NISSAN ALTIMA

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.

3 NISSAN ALTIMA owners have reported this issue to NHTSA across model years 2005. Most reports come from the 2005 model year. The most commonly reported component is Engine And Engine Cooling (66.7% of reports).

Real NISSAN ALTIMA Owner Reports

Source: NHTSA Complaints Database

"I already went though p0420 issue few years back and i got it again. nissan dealer charged me whole lotta money to fix the issue and the warning sign came back again. went to local auto zone and it show p0420 again. please help."

— 2005 NISSAN ALTIMA owner · ELECTRICAL SYSTEM · Filed 11/25/2012

"This year i am required to obtain a smog test for my 2005 nissan altima tha i purchased used from power volvo in california. my car is throwing off a p0420 code which requires a replacement to the pre-catalytic converter."

— 2005 NISSAN ALTIMA owner · ENGINE AND ENGINE COOLING · Filed 09/29/2011

"Car arbitrarily stalled and cut off at low speeds and began to also jerk intermittently as if attempting to shut down while traveling at highway speeds...easily this could lend to a collision!!! service engine soon indicator illuminated on dash and has remained lit."

— 2005 NISSAN ALTIMA owner · ENGINE AND ENGINE COOLING · Filed 02/18/2009

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

📊 Complaint Trend by Model Year

3

'05

Common Causes on NISSAN ALTIMA

Based on NHTSA complaint component analysis for this vehicle.

ENGINE and ENGINE COOLING 66.7%

ELECTRICAL SYSTEM 33.3%

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 NISSAN ALTIMA? ▾

P0420 indicates: Catalyst System Efficiency Below Threshold Bank 1. This is a emission controls code. 3 NISSAN ALTIMA owners have reported this to NHTSA.

What are the most common causes of P0420 on NISSAN ALTIMA? ▾

Based on 3 NHTSA reports, the most commonly cited components are: Engine And Engine Cooling, Electrical System. These percentages are based on the component field in owner complaints.

Is P0420 serious on my NISSAN ALTIMA? ▾

Of 3 NHTSA reports for this code on NISSAN ALTIMA, none involved a crash or fire. However, any diagnostic code should be evaluated by a qualified mechanic.

What should I do if my NISSAN ALTIMA 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.