Why won't my car gu up hill

You have a failed transmission.

if you are selecting lower gears on a stick shift... good... if the car is automatic you should leave the shifter in drive position going up hills or towing. use lower gears to go down hills only. check the cooling fans for proper operation. also... their is a product or additive you can get called "Water Wetter" add this to the coolant to help the cooling system work better. Also, the engine thermostadt may me malfunctioning.

Reset the computer & check the fuel PSI. You may want to replace the gas filter. when u run dry, the filter picks up all the dirt at the bottom of the tank. Make sure your gas PSI is good before u get into electronics. start w the basics. That would set that code too trying to start dry.Good luck

check the rpm and road speed when this happens . The cruise control will increase to keep RPM constant but as the road speed drops the auto may be shifting down and as the rpm increase it shifts back before the rpm adjusts. You can override a cruise control in this situation by simply pressing down on the accelerator to maintain the power setting and road speed and when the situation is passed and you take your foot of the accelerator the cruise control will return the system to the set position without you needing to do anything

Mass air flow , crank sensor . I wouldn't discount anything . Having a scan tool that can view engine sensor data would be a great help too , testing fuel pressure and flow and back pressure test the exhaust .
058 Engine Hard to Start or No Start Lean Fuel Condition
055 Engine Hard to Start or No Start Scan Data for EGR
057 Engine Hard to Start or No Start Ignition Module Test
007 Catalytic Converter Testing

try turning the overdive button off if the problem goes away then its proprob. a tcc solinoid or the converter itself i would have it ckd 4 codes 1st and have the trans fluid flushed and and shudderfix avail. and most parts stores

clogged catalytic converter perhaps?

you need transmission fluid and your axle is broken

sounds like it may have a bad ignition miss. check spark plugs, wires, and coil packs.