My 2000 E430 just had a check engine light on today, but the display on the instrument says no malfunction. I checked the gas tank cap and it is very tight, battery is fully charged and the car is running fine as normal. I do not have OBD II scanner to read the code(s).
What are possible problems ? Oxygen sensor ?
Which auto part stores scan the code for free: Autozone, Pepboys or Kragen ?

__________________
'00 E430 Brilliant Silver/Ash

For unknown reasons, the CEL is off after driving back home from cash wash this morning. But the multifunction shows "lamp defective", swapping left and right brake lamps erases the defective lamp warning. These brake lamps were replaced about 2 weeks ago because one lamp was bad.

I'm buying a OBDII scanner so that I can read the error codes in the future.

__________________
'00 E430 Brilliant Silver/Ash