Question

2011 Ford F350 Lariat 4X4 6.7 L. with code P21AB. How do I fix and clear this fault code?

Answer 1

P21AB Reductant level sensor "B"

This is for the fuel additive system that supports the diesel particulate filter (DPF) to reduce pollution that is generated by diesel vehicles, The DEF tank unit has a heated temperature and a level sensor. ( DEF has a blue cap, and the fill cap varies by design). When you fill the vehicles tank the fuel additive module calculates and communicates this information to the reductant tank,this is the fuel level "B" in question either you have no reductant or the level is non op,

Answer 2

P21AB FORD Code - Reductant Level Sensor 'B' Circuit High

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