P0420 on TOYOTA TACOMA — Catalyst System Efficiency Below Threshold Bank 1

Q: "What does P0420 mean on a TOYOTA TACOMA?"

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

Q: "What are the most common causes of P0420 on TOYOTA TACOMA?"

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

Q: "Is P0420 serious on my TOYOTA TACOMA?"

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

Q: "What should I do if my TOYOTA TACOMA 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 TOYOTA TACOMA

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 TOYOTA TACOMA owners have reported this issue to NHTSA across model years 2006-2009. Most reports come from the 2006, 2009 model years. The most commonly reported component is Structure (50.0% of reports).

Real TOYOTA TACOMA Owner Reports

Source: NHTSA Complaints Database

"Toyota tacoma limited service campaign. i dropped my truck off in november 2015 for a frame inspection, i was then told i could not drive my truck off of the lot and had to have a loaner vehicle. i was in a loaner vehicle without my truck for 4 months until the beginning of march 2016."

— 2006 TOYOTA TACOMA owner · STRUCTURE · Filed 03/02/2016

"Check engine light: p0420 fault code. also, there is a rattling sound and exhaust back up to the pressure release mount where the exhaust connects to the engine. dealer diagnosis catalytic converter is failing, replacement required also the heat shield is ratting."

— 2009 TOYOTA TACOMA owner · ENGINE · Filed 01/28/2019

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

📊 Complaint Trend by Model Year

1

'06

1

'09

Common Causes on TOYOTA TACOMA

Based on NHTSA complaint component analysis for this vehicle.

STRUCTURE 50%

ENGINE 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 TOYOTA TACOMA? ▾

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

What are the most common causes of P0420 on TOYOTA TACOMA? ▾

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

Is P0420 serious on my TOYOTA TACOMA? ▾

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

What should I do if my TOYOTA TACOMA 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.