Overhaulin' - Why would the check engine light be on after engine replacement?

Why would the check engine light be on after engine replacement?

I don't know anything about the car, it's for sale but it has a new engine. Why is the engine light on? The person selling for a friend said it was because of a sensor problem. It's such a pretty BMW....:-( talon699, you gave me a laugh, because I know what you said is true but I don't want to believe it. Well, don't buy it until fixed or until you know what the problem is. Eddie, I'm totally listening to this advice.

Public Comments

u ight need to change the oil or get new oxygen sensors. just take it into firestone or something
It is one of the emission control sensors. More than likely it is a bad oxygen sensor. Take it to an auto parts store and let them read the computer codes for you and tell you what the problem is. Then you'll know about how much it will take to fix it.
Well, don't buy it until fixed or until you know what the problem is. Autozone or other auto parts place will check the code and let them know what is actually wrong. It could be something as simple as the gas cap not tightened properly all the way up to a bad engine / transmission. Make sure it is fixed before you attempt to buy or at least make sure you know what the problem is and how much it will cost to fix it.
The check engine light is for issues related to engine management (input from all the sensors). It's possible that when the engine was changed, they missed reconnecting a sensor, or one was damaged during the engine swap. The light will not tell you if there is a mechanical issue with the new engine. If you are seriously considering buying this car, you need to find out why the engine was changed in the first place. Personally, I would be very cautious of a car like this. If the engine was damaged due to abuse or neglect, what else could be wrong with the car? There are plenty of cars for sale out there - I'd suggest you keep looking.
maybe when they replaced the engine they left a sensor unhooked.
Try the gas cap. On some cars if the gas cap is not screwed on correctly the engine light can light up. Ive had a car before in the past and my mothers current car does that.
You do know that BMW stands for Break My Wallet. If it has a new motor and is less than 10 years old , run away. Just because it is "pretty" is not a reason to buy a car. Especially a BMW. Don`t buy a car from someone who is selling it for a 'friend' . You are asking for trouble