Dealing with P0421 issues on our Hino 268 fleet

[Maxwell1]

I'm trying to sort out a recurring P0421 "A/T/C Below Threshold" code on several of our Hino 268 trucks. The dash light comes on, but the code stays inactive. I've heard certain models might trigger false alerts, anyone seen this?

 

[abracadabra]

I'm trying to sort out a recurring P0421 "A/T/C Below Threshold" code on several of our Hino 268 trucks. The dash light comes on, but the code stays inactive. I've heard certain models might trigger false alerts, anyone seen this?

Yeah, that code is a little common on the 268s even when things seem fine. It's highly likely to be lazy sensors or a regen issue. Maybe you could go check if there are any software updates or ECM reflashes.

 

[Maxwell1]

Good call, I'll check on possible ECM updates. We've done regen cycles recently, but lazy sensors might be the culprit, it's weird how the code's inactive but still trips the light

 

[Untamed_]

How do you diagnose and fix a recurring P0421 "A/T/C Below Threshold" code on Hino 268s when the code shows up inactive..could it be a sensor issue, or is this a known false alert on certain models?

 

[MightyHino]

If your P0421 light is on but inactive, it might be a sensor issue or a computer problem. Try updating your system and checking the sensors after the regeneration cycles