Medium and Heavy Trucks
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Thanks for asking your question. I will try and help you out.
Unfortunately I have seen this code many times.
The 3711-31 indicates the inlet temp of the DPF is less than 1000 degrees F. When this happens the soot in the DPF can not be incenerated so the regen will stop.
This problem can be caused by several things.
First is clogged fuel filter fittings. I would change these first.
Second is a faulty are head.
Lastly is a lack of combustion air. If this is the case normally there is a code for low combustion air.
Please reply back if you need more help or have more questions. I am happy to assist.