NOx Converting Catalyst Conversion Efficiency
The HINO-P20EE (Hino) diesel fault code means: NOx Converting Catalyst Conversion Efficiency. This is a serious severity code.
- Keep driving?
- Short distances only
- DIY difficulty
- intermediate
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What Are the Symptoms of HINO-P20EE?
- Check Engine light
- Possible engine output and speed restrictions if it persists
What Causes HINO-P20EE? (Most Likely First)
- Deteriorated SCR catalyst High
- DEF dosing too high or too low (injector, pump, DEF quality) High
- NOx sensor fault or a temporary condition such as frozen DEF (Hino SB-15-041) Medium
Can I Still Drive with HINO-P20EE?
Short distances only. HINO-P20EE is rated serious severity. Keep trips short and get it diagnosed soon rather than waiting for symptoms to worsen.
Frequently Asked Questions
What does P20EE mean on a Hino?
P20EE means NOx Converting Catalyst Conversion Efficiency. SCR catalyst deterioration is detected as a drop in purification efficiency calculated from the upstream and downstream NOx sensors: with exhaust flow 500-1,000 kg/h, SCR catalyst at 210-260 °C, upstream NOx under 200 ppm and the burner off for 60 seconds, the target conversion efficiency minus the measured average is 1.0 or more. Too much or too little DEF dosing also lowers the efficiency.
Is P20EE a Hino-specific code?
P20EE is an SAE-format powertrain code, but the title and the conditions here are Hino's own, read from Hino's service documentation, not a generic definition.
Mechanics Guide Step-by-step diagnosis
How Do You Diagnose HINO-P20EE?
Follow Hino SB-15-041: inspect the upstream and downstream NOx sensors first.
Check DEF quality and the DEF injector.
Inspect the SCR catalyst with the diagnostic tool.
Sources 3
This page is built from documented references. Verify against your own service info before repair work.
- Hino Workshop Manual, HINO 238 / 258LP / 268 / 338 series with J08E-VB and J08E-VC engines, Engine Control System (J08E) chapter, DTC P20EE "NOx Converting Catalyst Conversion Efficiency"technical description and detection conditions. Distributed through Hino's dealer service portal; no public link.
- Hino service bulletin SB-15-041 (filed with NHTSA)correction of the workshop manual troubleshooting procedure for P20EE, 2015-2016 Hino conventional trucks
- SAE J2012Diagnostic Trouble Code Definitions (defines P20EE as a generic OBD-II code)
P20EE on Other Platforms
The same code ID appears across other engines, vehicles, and equipment. Diagnostic flow varies by platform — see the matching breakdown:
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