I got the engine codes P1406 and P1401 on my 2001 Ford F150 4.6L V8. I change that sensor and it lasted 2wks and the light came back on
P1406 EGR downstream pressure hose
P1401 DPF(differential pressure feedback) EGR circuit malfunction
Check the hose that the sensor connects to. with engine running exhaust should be able to come out, Either the hose got plugged or the pipe is plugged.
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