metro2084

I've started the car this morning, seemed that it took a second longer than usual. Then I realized I couldn't switch gears. I connected the obd reader and it gave me P20BD: reluctant heater "B" control circuit/open.
I turned off/on the car couple times and was able to switch gears but was scared it won't work later, and so i don't get stranded. Fast google search says it might be auxiliary battery? Should I try replacing it first or should i go straight to mechanic?