What does this code mean?
The wording below belongs to the named make and communication. Match the complete code, reporting module, model year and engine before applying it.
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.
P0421Catalyst efficiency below thresholdManufacturer communications
4Original wording in English
HINO
Reported code forms P0421
AA0H0 A subject vehicle may exhibit an illuminated MIL (Malfunction Indicator Lamp) with DTC (Diagnostic Trouble Code) P0421 (ATC Deterioration Monitoring). The engine ECU may falsely detect an issue with the ATC (After…
HINO
Reported code forms P0421
SB-15-003 CORRECTION OF WORKSHOP MANUAL FOR HINO 2015MY (REVISION OF TROUBLESHOOTING PROCEDURE FOR THE DTC P0421)
HINO
Reported code forms P0421
A subject vehicle may exhibit an illuminated check engine lamp with DTC (Diagnostic Trouble Code) P0421 (Catalyst efficiency below threshold). The engine ECU may falsely detect an issue with the ATC (After Turbo…
HINO
Reported code forms P0421
SB-14-012 A subject vehicle may exhibit an illuminated check engine lamp with DTC (Diagnostic Trouble Code) P0421 (Catalyst efficiency below threshold). The engine ECU may falsely detect an issue with the ATC (After…
Check vehicle applicability
14A listed vehicle is a research lead. Confirm the engine, production range and software in the manufacturer's information.
| Make | Model | Model year |
|---|---|---|
| Hino | NE8J | 2019 |
| Hino | NE8J | 2018 |
| Hino | NE8J | 2017 |
| Hino | NE8J | 2015 |
| Hino | NE8J | 2014 |
| Hino | NE8J | 2013 |
| Hino | NE8J | 2012 |
| Hino | NE8J | 2011 |
| Hino | NE8J | 2010 |
| Hino | NE8J | 2009 |
| Hino | NE8J | 2008 |
| Hino | NE8J | 2007 |
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.
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.