I’ve been playing with the json code you posted above and I kept getting errors on rendering it until I realized that the double-quote marks that you are using aren’t standard text marks. If your website actually returns that data like that then you will have to figure out how to convert it.
Here is the code I used in the template editor to test what you want to do and it worked:
{% set value_json =
{"version":"B","tme":"0510181934","rbc":"11","rbt":"28449326","car":"2","amp":"16","err":"0","ast":"0","alw":"1","stp":"0","cbl":"32","pha":"63","tmp":"28","dws":"33128","dwo":"0","adi":"0","uby":"0","eto":"180","wst":"3","nrg":[229,231,234,2,44,0,0,0,0,0,0,7,7,3,1,30],"fwv":"024.2","sse":"001891","wss":"Home Benissa","wke":"**************","wen":"1","cdi":"0","tof":"101","tds":"1","lbr":"40","aho":"3","afi":"7","ama":"32","al1":"13","al2":"16","al3":"28","al4":"30","al5":"32","cid":"255","cch":"65535","cfi":"65280","lse":"1","ust":"1","wak":"x","r1x":"2","dto":"0","nmo":"0","sch":"AAAAAAAAAAAAAAAA","sdp":"0","eca":"0","ecr":"0","ecd":"0","ec4":"0","ec5":"0","ec6":"0","ec7":"0","ec8":"0","ec9":"0","ec1":"0","rca":"x","rcr":"","rcd":"","rc4":"","rc5":"","rc6":"","rc7":"","rc8":"","rc9":"","rc1":"","rna":"","rnm":"","rne":"","rn4":"","rn5":"","rn6":"","rn7":"","rn8":"","rn9":"","rn1":""}
%}
{% if value_json.car == '1' %}
disconnected
{% elif value_json.car == '2' %}
connected
{% endif %}
Notice the difference between your double quote marks and mine.
And once you get that sorted out the just continue on with the if statements to return values you want based on the key value you select.