I recently had to have a 7 year old battery replaced on my 1997 Acura 2.5 TL. The first battery I bought as a replacement seemed fine for a few days, then it stranded me. I called the tow truck a second time and returned to the store. They tested it - it gave a different reading every time they put the tester on it - and finally gave me a new one after checking to see if the alternator was working (it was). The newest battery seems to be working as intended. Even though it has 182,000 miles on it and has had minor issues because of its age, the car has been running pretty well. The next time I drove it after replacing the battery, the check engine light came on and has stayed on. I had also refueled on the way home from the auto parts store, so I thought it might be the gas and would resolve itself soon. When it did not, I bought more gas and used a fuel treatment designed to help if there is water in the gas. The light is still on. Since I am on a fixed income and the towing and battery replacement ate up a lot of money (for me), it will be another two weeks until I can begin to think of having even minor work done on my car. Is it safe to drive? It seems to be running okay. Could the battery replacement be the issue, or is the timing a coincidence?
A solid check engine light is okay to drive but means soon you should service it. If things align right it may go out after 4 drive cycles.
Some autoparts stores read the actual code for free which you take exact one (eg P401) and post back here for “free” help.
The Check Engine light is probably on because the readiness monitors haven’t reset themselves. When the battery was disconnected, the computer lost all it’s adaptive memory or learned parameters. In order to reset the readiness monitors the vehicle has to go thru what are called drive cycles. So drive the vehicle for a while and see if the Check Engine light goes off. If it doesn’t, have the codes retrieved from the computer. Some parts stores will do this for free.