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.
P043000Catalyst system Bank 1/2, Efficiency below thresholdManufacturer communications
5Original wording in English
AUDI
Reported code forms P043000
This bulletin provides information regarding a software update for DTC P042000 and/or P043000.
AUDI
Reported code forms P043000
TSBs in this newsletters include the MIL on due to DTC P042000 and/or P043000 (Catalyst system Bank 1/2, Efficiency below threshold) being stored in the ECM. New ECM software implemented to correct the condition.
AUDI
Reported code forms P043000
The MIL is on due to DTC P042000 and/or P043000 (Catalyst system Bank 1/2, Efficiency below threshold) being stored in the engine control module (ECM), J623 (address word 01). The diagnostic limitations were too narrow.…
AUDI
Reported code forms P043000
Supersedes Technical Service Bulletin Group 01 number 15-26 dated June 30, 2015. The MIL is on. DTC P042000 and/or P043000 (Catalyst system Bank 1/2, Efficiency below threshold) is stored in the engine control module…
AUDI
Reported code forms P043000
The MIL is on. DTC P042000 and/or P043000 (Catalyst system Bank 1/2, Efficiency below threshold) is stored in the engine control module (ECM), J623 (address word 01). The diagnostic limitations were too narrow.
Check vehicle applicability
1A listed vehicle is a research lead. Confirm the engine, production range and software in the manufacturer's information.
| Make | Model | Model year |
|---|---|---|
| Audi | A8 | 2012 |
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.