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I have a 3 month old 992.2 and put it on a Ctek MXS 5.0 charger/maintainer for 3 weeks and just removed the charger and wanted to take the car for a spin. The car started but I now have an Auto Start/Stop Failure warning on the dash. I backed out of that to see the engine stats and it says the Voltage is 15.0. Is that normal? I have an AGM battery. I also have a yellow engine light on the dash. Is my Ctek causing this? Car ran beautifully previously. Thanks.
Your battery seems to be overcharged. The Ctek should turn off/stop charging at 14.9V and then wait for the battery to discharge before kicking in again.
From what I know the car will charge it up to 14.6V to 14.8V.
Typically 15v and above is considered bad for a battery.
Likely unrelated to the charger, 15V is normal when the alternator is charging and it's cold.
If the battery was fully charged by the Ctek, voltage should have dropped off to normal 12-13V range quickly.
I just restarted the car after letting it sit a while. Now the voltage is 12.1 and the Auto Start/Stop failure warning did not show up....and it works fine.
But I still have the check engine symbol....when I first started earlier today, I recall a bit of a sputter, but now when I start, it seems fine. Any thoughts what can be causing the check engine? Is it a problem driving with that showing given the engine is running smoothly?
Yes. First time using the charger. It went to level 7 and all seemed fine. I think the charger caused all this. I just drove it again today and now the check engine light has turned off.
NYCA noted above that the BMS will take some time to reset. I think he is correct and that is what happened. Now the check engine light is off and the car runs perfectly. I am thinking the charger over-charged the battery. That is why the voltage was 15.0 when I turned on the car right after I disconnected the Ctek and started the car, which was sluggish/misfiring. Now the voltage fluctuates around 12 to 13 volts on the dash . I don't think I'll be using that charger again.
@Rschnei I do not think you CTEK charged your Battery to 15V. The dash reading is clearly showing your engine running and the alternator charging your battery at 15V, as your engine is idling at ~630RPM
The Start-Stop Failure is most likely do to an under charged battery or one that has a charge that does not match what the BMS expected. As @WCE stated: "15V is normal when the alternator is charging and it's cold."....
What was the battery voltage BEFORE you started the engine? In the end, I an glad that it all worked itself out. No need to toss your CTEK charger.
Usually you can restart the car and it goes away. I'm pretty convinced its a battery issue, I'm going to try and get mine replaced soon, happens occasionally even if battery is charged.
It's kind of stunning how many faults on these forums seem to be the results of the battery being low in these cars. After driving for 2 hours so the battery should have been topped up, my new 992.2 was able to play YouTube on just the single PCM center screen for only ~25 minutes before it told me it was shutting it down due to low battery. I threw my NOCO maintainer on the cigarette lighter just to keep watching YouTube on it. This shoebox sized AGM battery has considerably less auxiliary power than your average laptop. That said, it's never failed to start the engine immediately for me.
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Removed Ctek Charger--Now Getting AutoStart/Stop Failure
