why does battery drain with ignition off?

Question

My vehicle dose not pass smog do to code po171 bank1 lean. My question, why does my new battery drain with car not started over night?

Answer 1

P0171 might be related to dirty/bad mass air flow sensor (you can try to clean it with mass air flow sensor cleaner) intake leak, bad oxygen sensor and so on

Possible causes

- Intake air leaks

- Faulty front heated oxygen sensor

- Ignition misfiring

- Faulty fuel injectors

- Exhaust gas leaks

- Incorrect fuel pressure

- Lack of fuel

- Faulty Mass Air Flow (MAF) sensor

- Incorrect Positive Crankcase Ventilation (PCV) hose connection

 

The battery is being drained, due to something staying on, like a bad switch that is staying on, bad radio and so on 

the problem is called Parasitic Battery Drain (Key Off) 

see video below which will help you diagnote the problem, you will need a multimeter