check engine light
 

I have a 99 m320 and the check engine light came on, I just had the oil changed got home and it came on. Any suggestions?

RE: check engine light
 

IT SOUNDS LIKE YOUR OXYGEN SENSOR IS BAD. ONE WAY TO TELL IS TO PULL THE NEGATIVE CABLE FOR 20 SECONDS , THIS WILL CLEAR THE CODES AND THE CHECK ENGINE LIGHT SHOULD BE GONE ,IF IT COMES BACK ON IN A COUPLE OF DAYS ITS YOUR OXYGEN SENSOR.

RE: check engine light
 

The check engine light is for emission faults, so you may be right, I dunno. But why do you think an O2 sensor is bad? I'm wondering what led you to that conclusion? Which O2 sensor do you think it is? There are four O2 sensors, no? Pre-cat left and right, and post-cat left and right? Maybe just two? Pre-cat and post-cat? I'm not sure what the exhaust system configuration is on a '99 M320.

If an O2 sensor is bad, pulling a battery cable won't fix it. Moreover, if one or more are bad it won't take two days to turn the light back on. As soon as the engine reaches operating temperature the light will come on if a sensor is bad. If it takes two days I'd say the sensors are working because an emission fault is detected by an operating sensor during that period.

I'm not against removing a battery cable to see if the light was turned on either in error or a temporary Mercedes-Benz brain fart condition. It happens. But if you want to know what the problem is without guessing, the car needs to be taken to a mechanic who can read the fault code(s).

RE: check engine light
 

I agree. The check engine light is on for a reason. It could be as simple as some ran the engine with the gas cap off or could be a sensor gone hay-wire. Taking to a good mechanic is the only way to find out. I say a good mechanic because would you like to take it a bad one ?

RE: check engine light
 

IF YOUR TALKING ABOUT ML 320 CHECK ENGINE LIGHT ON
WHEN THE CHECK ENGINE LIGHT CAME ON WAS THE CAR RUNNING OR IDLING FUNNY
AND WHEN YOU TURN THE KEY OFF AND STARTED THE CAR THE CHECK ENGIN KIGHT IS STILL ON BUT THE CAR IS RUNNING BETTER IF SO YOU HAD AN ENGINE MISSFIRE
ADVICE IS TO GO FOR SVC AND TO SEE WICH CYLINDER THAT CAUSUNG THE MISSFIRE