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Exhaust Gas Recirulation - EGR
EGR Valve clogged or defective.
EGR Passages clogged with build up.
Insufficient flow also includes your passages in your intake. Upper would be your plenum.
Vacuum lines can trigger this too.
Exhaust leak(s) are a major player.
Never heard of a fuel pump/filter tripping P0401
Exhaust Gas Recirulation - EGR EGR Valve clogged or defective. EGR Passages clogged with build up. Insufficient flow also includes your passages in your intake. Upper would be your plenum. Vacuum lines can trigger this too. Exhaust leak(s) are a major player. Never heard of a fuel pump/filter tripping P0401