My 2000 Ford Windstar failed the emissions test with (3) codes. on 2000 Ford Windstar

P0135-02 Heater sensor heater circuit malfunction bank 1 sensor 1, P01131-Manufacturer specific code, P0171-System too lean bank 1.

1 answer
THE PO 171 IS POSSIBLE VAC LEAK IN BANK 1, HEATER CIRUIT POSSIBLY BAD IN SENSOR OR CIRCUIT