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Re: Paccar MX13 P3901
Posted to HD/Fleet Forum on 2/22/2021 2 Replies

Hello James B.,

I have dealt with a lot of DEF issues on Farm tractors (systems are similar) and this problem has usually led back to DEF crystal formation in lines or connections. The pump is trying to draw DEF and it is not getting it so it goes into negat... Login to read more.

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