P0420 P0171 Toyota Corolla 2003

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Reynaldo · Answer 1 · 2018-12-02T06:21:05+0000

P0171 Fuel trim lean Bank 1

P0420 Catalytic below threshold

Do a MAF cleaning, and inspect the MAF air duct for any tear that would cause a lean code condition

A typical MAF air duct

A tear like this would affect the operation of the MAF, and set a lean code condition,