Hello everyone! I have a 2000 ML 430 and every time i put gas in it the check engine light will pop on soon after. Then when the truck get around 1/2 tank the light goes out and stays out until i fuel up again. Happens like clock work. I had autozone run the codes and received the very popular p0170 and p0172 ( mass air) but why would the light go out at 1/2 tank if the mass air sensor was bad. I have also looked over all vacume lines and they look fine. Please help. I don't want to spend a ton of $$$ but would like to get it fixed. My pregnent wife drives it and winter is on it's way here in michigan. If the truck stops running with her in it i will not be happy.

Thanks,
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