What does this code mean?
The controller judged catalyst performance below its threshold under the monitor's test conditions. P0420 refers to bank 1 and P0430 to bank 2. Inspect exhaust leaks and related misfire or mixture codes; assess sensor signals and the vehicle-specific catalyst test. The code alone does not prove the catalyst or an oxygen sensor needs replacement.
Sources and interpretation [1]
A code identifies a detected condition, not a part that must automatically be replaced.
Manufacturer wording
Source wording can vary by vehicle and suffix. It is shown as written, not as a universal diagnosis.
P0420THREE WAY CATALYST FUNCTIONP0420TW CATALYST SYS-BIManufacturer communications
4Original wording in English
NISSAN
Reported code forms P0420
NISSAN: DTC P0420 (TW CATALYST SYS-BI) STORED IN THE ECM. CONFIRM THIS BULLETIN APPLIES-CHECK THE CURRENT ECM PART NUMBER; COMPARE YOUR CURRENT ECM PART NUMBER TO CHART A. REPLACE THE EXHAUST MANIFOLD CATALYST;…
NISSAN
Reported code forms P0420
THIS BULLETIN PROVIDES INFORMATION ON VEHICLES EXHIBITING A MALFUNCTION INDICATOR LAMP ON WITH DIAGNOSTIC TROUBLE CODE P0420 CATALYST SET. *TT
NISSAN
Reported code forms P0420
SUBJECT REGARDING MALFUNCTION INDICATOR LAMP ILLUMINATED WITH DIAGNOSTIC TROUBLE CODE P0420. *JG
NISSAN
Reported code forms P0420
VEHICLES UP TO 1N6DD26Y9WC347717 MAY EXHIBIT A MALFUNCTION INDICATOR LIGHT ON WITH DIAGNOSTIC TROUBLE CODE P0420 (THREE WAY CATALYST FUNCTION) STORED IN THE ECM AND / OR EXHAUST RATTLE NOISE. *TT
Check vehicle applicability
5A listed vehicle is a research lead. Confirm the engine, production range and software in the manufacturer's information.
Before replacing a part
Record codes and freeze-frame data. Check battery condition, related codes and visible wiring or hose damage. Follow the vehicle's diagnostic procedure and test results before replacing parts.
Sources and interpretation
These explanations are editorial summaries of the linked manufacturer material. PDF page numbers count from the first file page. Original publications are in English; translations are reference aids. A cited edition is not a claim that it is the manufacturer's latest instruction.
- 2024–2025 MY OBD System Operation Summary for Gasoline Engines ↗
Ford Motor Company · PDF page(s) 2, 3 ·
Source check date · 2026-10-27
Can I keep driving?
A code alone cannot establish whether driving is safe. A flashing malfunction light, severe shaking, overheating, oil-pressure warning or loss of braking or steering needs prompt attention. Stop in a safe place and seek assistance when control or engine safety is affected. Follow the vehicle handbook.