P240F active to inactive

JHC

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2016 Hino 268
Check engine light came on with the SVS at about 35mins of driving. The engine self check produced a P240F code. The SVS light has since turned off and the code has moved to inactive status by now but the check engine light stayed on. Any thoughts on how to clear the light? Is it still worth a trip to mechanic since it has gone inactive?
 

greasytshirt

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P240F is essentially an EGR performance code. It does not blame any specific device, instead there are a number of things that need to be inspected and confirmed for an accurate diagnosis. Engine performance can be affected, so you need to get it looked at.
 
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JHC

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Thanks for weighing in. Code actually went back and forth between active and inactive over the course of 2 days and I went into semi-limping mode (hammer down on a flat straight away and barely getting 60) Turned out to be NOx sensors, one burned out and one blinking. 2 hours and a mint to replace. Guess I need to increase the maintenance allowance in the budget haha
 

greasytshirt

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Did you mean P204F? That is a much more common code where NOx sensor replacement makes sense.
 

JHC

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Sorry…fat finger error. Looked back just now at a pic I snapped of the truck’s report on inactive codes. 204, not 240.
 

greasytshirt

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I read it as P204F, wrote a reply, re-read what you wrote, looked up P240F, erased my previous reply and wrote a new one. So now I'm rewriting it again. Awesome.

P204F is a generic code put out by the ECU when the DCU requests the check engine light. The DCU controls things like DEF injection and NOx sensors. Many of the codes trigger limp mode, so P204F needs to be addressed more urgently than some other things.

Unfortunately codes in the DCU can't be read from the dash.
 
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