i have a 06 cls500. so basically it been having a battery issue , where something in the car is draining the battery so every night if i use the car and i’m done with it i would take the battery off , been doing this for like 2-4 months , so now 2 weeks ago i went to the car and it was dead , i had someone directly give me a jump with cables and for about 10/15 and it finally started after fixing the terminals quite a bit just moving it around , then it finally turned on after a long battle. i drove it around for about 10 mins so the car would catch itself i seen the gas tank is low but the gas light didn’t come on so i parked it and rolled down all the windows and turned the car off and it was off for 5 minutes and i tried turning the car back on and they key didn’t turn at all in the ignition hold , it was stuck in one place and the wheel was locked also , i can’t move the gear box , lights would turn on in the car but the headlights are dim , and on the dash it sometimes says does not recognize key , tried changing the battery in the key still nothing changed. the car would not crank or turn over at all just lights inside sometimes and headlights are dim , and on the dash it sometimes says “reduce brake” . i went on youtube and google to see what might be the issue and all i’m seeing is the EIS the electronic ignition system and the starter relay.

Well you have several issues going on. First you need to check alternator output. If voltage is 13.8-14.2 alternator is fine. You got it started so that rules out starter issue. How old is your battery? May need it changed. If lucky they last 2 years and you change both not just one. Then the drain. I had two one in the audio gateway which I bypassed the other in the ignition subsystem which turned out to be a sticking relay because the drain was intermittent. Get a light bulb and hook it between the battery terminal and the post in series. Then pull one fuse at a time and see which one dims the bulb when pulled. You got work to do but the car is quite repairable. good luck