Please take a moment to click user cp and edit details so you can easily add your vehicle and location to your profile; it's often useful information when you're seeking assistance.
As an aside, I find it curious that while you have an ML (either a W163 or a W164) you chose to post your question in a 12-year-old thread about tires on a CLK (W208) rather than in the forum that is native to your vehicle. There is also a dedicated forum here that focuses on tires and wheels.
In any event, no, you won't damage any of the computers on your ML by running an undersize tire, at least so long as you run it on all four wheels. However, it's odd that you only focus on that one single aspect of running an incorrect size tire. Let's look at some of the other issues, both real and potential.
Smaller tires have to spin faster for a given road speed. This means you will rack up more miles on your ML than you actually drive, and your speedometer will be reading fast (meaning you will be driving slower than your speedometer indicates). Ultimately this also means that when it comes time to sell your truck, you won't be able to verify that the mileage shown on the odometer is correct, even though it will be too high overall (meaning that the value of your SUV is lower due to more miles). Too, you're effectively altering the final drive ratio for your ML, meaning that you may also suffer a loss in fuel economy (you're more likely to notice this on freeway miles rather than around town).
It is also possible that those tires may also be too narrow for the stock wheels on the ML. You would have to check that against the tire manufacturer's specifications for that tire model and size. Even if they are safe to use on your wheels, you will likely have to modify the proper operating pressure for the tires. (Probably you will need more air resulting in a harsher ride.)
Finally, you will be reducing your ground clearance by a small amount (roughly a half-inch). If like most SUV owners you only drive on improved roads, that's no big deal, but if you venture off-road (or have to drive in snowdrifts) that becomes a concern.
All things considered, it's really not worth it.
What is wrong with just using the proper size tire? If it's because "I found a deal on this size," that's really not a reason. You can buy cheap gas and junk oil for less, too, but that's not the way to maintain your vehicle. Moreover, you'll have these tires for many thousands of miles. It's possible that whatever you save will be eaten up by the added cost of fuel alone.
Just some food for thought.
Good luck. See you in the ML forum, it's the best place to get help for your questions about your ML.
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