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Q: Engine Computer Issues (spark plugs & coils were changed 5 months ago as well).

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About 6 months ago my eml/service & brake lights came on. The car started running rough & wouldn't go over 50mph. I had car towed to mechanic. After much investigation, the mechanic said the engine computer would need replaced. He didnt do this without much investigating. He is the local mechanic who does all imported cars in my city. He gets very high remarks from customers. He purchased a new computer from the BMW dealer. He did the programming and installed the unit. I got the car back and all was good. Last week, out of nowhere, when I started the car, the eml/service lights came on. The car was running rough again. This time the lights didn't always come on at startup. When not on, the car would run perfect. Car is back to mechanic. The codes he is getting are saying the eng. computer is a problem. He is still investigating because he doesn't understand how this happened. I am very confused too. Any ideas on what could be happening and what we should do? Help?

My car has 80000 miles.
My car has an automatic transmission.

Do you have ANY aftermarket electrical equipment in the car? Such components can impact the function of the PCM. Also, check the alternator output and stability. If the power supply to the PCM is not within specification, that could damage or alter normal function of the PCM. Check for defective, inadequate, or missing ground wires and terminals as well.

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