Found a trick recently regarding the istop malfunction warning.
Yesterday, out of no where after doing my shopping, the warning symbol showed up. So double confirm from the error menu pointing to the istop malfunction. The car still can crank up without hesitation, so was a little perplexed.
So on the way back, got a long stretch of open road and drove rather swiftly averaging above 100km/h till i reached home. A slight sigh of relief as no need to call in tow truck.
I reached home, trying to figure out where could possibly go wrong. So i restart the car in accessory mode. And to my surprise, the warning symbol disappeared. Go check in the error log, also no longer listed. I fired up the car another time just to double confirm, also no more error message. Feeling much relieved, but still i took the precaution by putting the battery to charge with a dedicated lead acid charger.
So a short conclusion, if you see this error initially, it could mean the battery is low on charge but not to the point of dying. Just not enough charge to support stop/start function. Try giving the car a good run on the expressway for 15 to 30 minutes. A good long stretch of swift driving can help put more charge back to the battery.
Not a fool proof method, but give it a try before spending few hundred for a battery replacement.
The i-stop error indication just means that the battery is unable to support i-stop. It is still good enough for starting your car.
The i-stop error will disappear after using the car for a while. However it will re-appear again. This on/off error will continue for a while until the battery deteriorates further and it becomes permanently on. (For me it took about 2 months). However starting your car is still not affected. You can then decide whether to replace the battery or not.