Collin Gannon

2016 C3oo 4matic, less than 300 miles. Check engine light came on. After research, might be gas cap (had filled up for the first time the day prior). I have now messed with the cap and think it is back on flush (although, I thought I had done that after filling up). How long until the system resets itself, usually? Just hoping it is resolved, and will not need to attend my scheduled service appointment.

Also, do they normally run with an engine temperature that registers at >80 on the engine temp gauge?

TSchuettinger

Have you been using the correct kind of gasoline?

BenzC400

It's normal for the temp gauge to read just above 80. I have a C400 that always reads one or two marks over 80. Every C300 loaner I've driven was exactly the same.

Collin Gannon

Yes, I did use premium.

Mikey53

With a brand new car, I'd get it into the dealer ASAP just in case.

TSchuettinger

What about any performance issues? Do you notice any odd sounds, rumbles, smells, misfires, bad fuel economy, ect.....? I'd definitely invest in a scan tool because they pay for themselves. They're really helpful if you plan on keeping the car past warranty (cars of this caliber are pricey to diagnose). You plug it in under the dash and if there's any fault codes, it'll give you a fault code then you can look up the code on the web and you'll know what's wrong before you show up to the mechanic. It's hard to imagine there would already be an issue with sensors or practically anything else. That's why I asked if you were using the right gasoline. I'd guess your car just needs a software update.

Mike5215

It's likely the a loose gas cap flummoxed the O2 sensor into throwing a fault. The dealer can clear it for you.

Collin Gannon

Thanks. I can't say I have noticed anything wrong with performance, and I was under the impression that I used the right gasoline. But, now I am getting a "check brake pad wear" message, and a "brake" light came on for about ten seconds as I was driving today.

For reference, I am not driving this car like a maniac. These lights and warnings are disconcerting, and dealer cant get me in until Tuesday.

Mike5215

That sounds more involved than an O2 sensor fault. Can you drop off tomorrow morning and get a loaner until they can get to it?

Collin Gannon

Iv left a message with the dealer's service department to do just that, hopefully it works out. As well, I got a scanner and did the code scan, and the car isnt throwing off any codes. I suspect the dealer will determine it is a software issue, perhaps?

Will update when the dealer has looked at the car.

Collin Gannon

Turns out it was a software issue with the check engine light, a fault that has affected other c300s at the dealer. They reset it and said the update would be ready in a month or so, at which point I would need to go back in and have it updated.

The brake light was caused by a factory defective sensor. In all the fix took less than an hour.

TSchuettinger

I knew it! Those computers sure are a pain aren't they?