2017 Hino 268 - J08E Engine - P0420 Code and Low Power

Question

My Hino box truck is struggling on hills. It feels like it's down about 50 horsepower. I'm getting P0420 (Catalyst System Efficiency Below Threshold). We don't do much highway driving, mostly city stop-and-go.

I've tried doing a manual regen, and it completes, but the light comes back the next day. I'm wondering if the Burner system (the AIB) isn't firing correctly to heat the DPF.

WeldShopWanda · Accepted Answer

✅ Confirmed fix: The Hino Burner system (AIB) had a clogged fuel nozzle and a cracked igniter electrode. It wasn't creating a flame to heat the DPF, so the truck was trying to regen but never actually burning the soot out. Cleaned the burner head and replaced the igniter and nozzle. Power is restored.

TurboTina · Answer

Check your VNT turbo actuator. If the vanes are sticking, you won't get enough boost, which leads to high soot production and P0420 codes as the catalyst gets overwhelmed.

2017 Hino 268 - J08E Engine - P0420 Code and Low Power

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