Where is the cabin air filter?

Won't start what do I look for

Car has to be cranked twice si it’ll start. Won’t start on first crank. Will start on second crank.

Don’t know where to plug the sensor plugs back up

When we replaced the water pump the oxygen sensors were unplugged from the back of the motor. You can’t see back there. I need either wiring schematic for the oxygen sensors or a picture of the back o…