Q: Why did my Check Engine Light come on after I replaced my battery?

An illuminated Check Engine Light can be caused by several different components. First, make sure the replacement battery is the right type for your vehicle. Then check that the vehicle is properly connected to the battery. You should also make sure that the battery terminals are clean, though with the battery being new, this shouldn’t be an issue. Then verify that your battery cables are clean, dry, and tight. If these things all check out, you can be reasonably sure that the issue is not because of the new battery. Luckily, with the Check Engine Light on, the computer will be able to tell you which system is having a problem. The next thing to do is to have the vehicle scanned for diagnostic troubleshooting codes. This can be done for free at most automotive part supply stores. A certified technician, such as one from YourMechanic, can also perform this scan, and sometimes even have better equipment.