it's not automatic. chances are, your oxygen sensor needs to be replaced (the car stores error codes, so you mechanic can check for sure). not an emergency, but you should probably get it taken care of next time you visit your mechanic.
My light came on at about 75K miles on my 1995 E320 and it was the oxygen sensor. It was quickly diagnosed and fixed at the dealer, because my INDY told me they didnâ€™t have the proper equipment to figure out the problem. As I remember, the bill came to about $400.00 US.
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