Here's the deal.

I need an inspection, and my guy said I won't pass if the CEL is on.
The CEL has been on for a while.

I am getting codes P 0171- Engine bank Lean
and
P 1870 - Transmission Component Slipping.

It is an automatic 2000 sunfire 3spd, 2200 engine.
What is causing my tranny to slip(could it be I need new tranny fluid? if not what else)
and do you think the transmission component slipping is causing the car to run lean, and thats why its throwing a lean code?
The gas milage is REALLY sucking, prolly like 15-18 MPG. Figured I'd ask here first before someone charges me a whole lot to check it out..

Any advice accepted. Thanks.

The full description for code P 0170 is P0171 Fuel Trim System Lean Bank 1

If it helps...

do u have an aftermarket intake? have you reset the code to see if it comes back on??

def first think you should do especialy cuz u get @!#$ty mileage it get the 1st o2 sensor its like 20.00 get an ac delco one if possible. ive had a new bosch with no problems but i def. have problems with there plugs i try to get oem whenever possible