What can it be on my Nissan Sentra the codes are PO715PO840PO845?

What if the check engine light is on in your 96 tercel you had it checked and they said it was the O2 sensor you replaced the sensor but the light is still on Does it need some time to reset or what? Where is the signal and hazard light flasher on a 1990 Isuzu Pickup? How often should you do a tune-up on a Mitsubishi? Where on a 1988 Mazda B2200 does the electric choke wire hook up? How tall is the 2013 Honda CR-V? What size speakers are in the front of a 1994 Nissan Pulsar TI model? What does it mean 2003 Honda Pilot blinking d light? Does the 1997 Honda Civic DX Hatchback have airbags? How much oil do you need for a 1985 Toyota corolla? How do you replace a starter on a 2002 Kia Sedona? When do you use overdrive in a 2002 Kia Spectra? Does the 1998 Nissan Pathfiner have a timing belt or chain? Best way to drain anti-freeze coolant from Honda civic dx? Which color antifreeze should you use in your 2001 Lincoln ls? How do you change a battery in a Toyota Echo? Land cruiser 200 series how to check auto trans oil? Replacement key for 1995 Mitsubishi eclipse? How do you replace the 100 amp fuse in the fuse box of a 2004 Toyota MR2? Replacing oxygen sensor on 2004 Suzuki XL-7? How many zeros does infinty have?

What can it be on my Nissan Sentra the codes are PO715PO840PO845?