2000 Ml 430 Cel
 

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,
I use a ton of online forums and this one is by far the best i have ever seen!

on other forums I've read that the first thing to check is always the gas cap. maybe you're not closing it tight enough?

I tried that.

I just ran up to the dealer and picked up a new gas cap. I will keep everyone posted on if it worked or not.

On my 2000 ML320 this happened when my MAF started getting weak. My guess is that the performance of your MAF is just marginal. MAF performance will continue to decline until it will no longer reset itself and you will end up having to replace it.