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2004 525i BMW 100k mls

My warranty just expired and I have a couple of questions.

1. Can the service advisory for spark plug replacement be reset at the instrument cluster or does it have to be performed by a dealer(changed plugs myself).

2. I drve very gingerly. Is it good idea to open it up on occasion to clear out the system?

  1. I’m not positive, but I believe you need a special tool to reset the service reminder.

  2. Clear out what system? Drive the car any way you choose. The computer will adapt to your driving style. There is nothing building up anywhere, and you don’t need to “blow it out.”

You need a “special tool” to re-set the service interval indicators (not a spark plug replacement reminder) you can buy this tool on the aftermarket.

Your number 2 concept/question is right out of times past and is firmly planted in automotive urban legends.

Is this your tool?

That tool is the general type of tool required, but the one shown in that link is for the older style BMW round diagnostic connector. A 2004 will have a rectangular connector.

For DIY, I suggest buying a tool that will also report any error codes stored in the computer. Those are available from Peake for around $180. I expect that there are other vendors with comperable tools available.

At 100k miles, you are about due for oxygen sensors on that car. There are four of them. They don’t all fail at once, but on my BMWs, I replace them all at once so that I know I am done with them for another 100k. If you start getting a check engine light some time in the next year or two, that will be the most likely culprit.

As for opening it up once in a while, opinions vary. If the car is fully warm when you do it, it won’t hurt anything. The engine has an RPM limiter and your drive train will handle far more than that '25 engine will dish out. Will it do any good? Doubtful. Best to use top tier gasoline or add a bottle of Techron every year or so to try to keep things clean. At 100k miles, it would not hurt to get some appropriate aerosol solvents and clean your mass airflow sensor, throttle valve, and idle air control valve.