tj99e320

I've read the threads about Check Engine Light, but I didn't find an answer to my question.

On my 99 E320, the check engine light comes on intermittently.
It comes on and goes away on an unspecific number of miles.

I'm trying to find a pattern, but I can't. I have no negative symptom:

1. I don't think it's the gas cap because when I remove it to fill up, I get that pressure release sound.
2. My performance is fine. It's not sluggish, it's doesn't jump.
3. My gas mileage is still 25+ per gallon.
4. I use Chevron 91 Octane.
5. I use Mobil 1 SAE 5.

The only think I'm irked about is the damn bright light being on...especially at night.

I think the first time I noticed it come on is after I gunned it at a light and the car sort of lurched.

Thanks for any insight. My nearest dealer is over 100 miles away.

As I understand it, the imission system is under warranty for 8 years or 80K miles. Would this be covered?

Thanks,
TJ

Stiggs

thats odd. My check engine light came on 2 days ago in my ML430. I was trying to park in the snow on my front yard...the tires were slipping and I gassed it pretty good. Next thing I know the light was on. Checked gas cap...tight as heck! Coincidence that it came on when I was hammering the throttle?? My dealer seems to think so!

Hank

A common problem is the O2 sensor.

MARK CUMMINS

Go Visit the Local auto zone They have a OBD scan tool that will Give the code then you wont have to guess

tj99e320

I just called my local Autozone and they said that they are no longer allowed to do free scans in California. Anyone else hear about this?

TJ

MB AMG

Mine in the W140 goes on sometimes. Maybe you need to take it for a service and you haven`t done so when it first came on. My ADS light always come on and i don`t know whyÉ

zam2000

Air Mass Sensor. It will run you around $250-300. Take about 2 min to install, so if anyone ask you more than $30, you may want to do it yourself.

EVERY Benz suffer this problem.

You need to reset the computer. Most place w/ ODB2 can do it for you for free (AutoZone). If not, you can do it by unplug the battery (for like 2 seconds). Make sure you have the radio code if you select to do it this way.

Again, it's the ODB2. It could be intermitment, eventually, it'll come on all the time. Best to fix it early. Make sure you have the computer read when the light come on, to make sure it's the problem. However, 99% chance is that it is.

tj99e320

Not 100% convinced my gas cap is okay (or perhaps hoping it is the main problem), I looked at it right after parking when I got to work today and I noticed the gasket had moisture on half of the circumference.

This could be an indication of a poor seal yes? Maybe?

Anyway, I loooked at some of the on-line sites for MB parts and I couldn't find the gasket. Has anyone ordered this before. Again, my nearest dealer is 100 miles away.

Thanks for all the input.
TJ

Light is still on, car is still running great.

Stiggs

here's a stupid question...how do I know if I have a bad air mass sensor? I guess I have to put all my faith in my dealership...they wouldn't lie ...right?

Say it is my air flow sensor or whatever....someone like me isn't going to just pop it in..I'm forced to pay 200-300 dollars because I don't know how to do that!

If its the gas cap....how much would that run. Thats where I'm placing my bets that there's where the problem is.

zam2000

Replacing the airmass sensor is actually easier than replacing air filter. And yes, you're just gona to unscrew one screw, and pop it in.

You have to read engine code when your check engine light comes on. When it's off, there's nothing to read.

Regardless, I would not have dealer doing this for you, they're likely charging you at least 400-500 dollars for doing this, not worth it. Dealer would say whatever it takes to make the most $$ out of your pocket.

The Air Mass Sensor cost around $250 at FastLane (mercedesshop.com). If you want to, buy a ODB2 code reader from eBay for $50. It helps to read and reset most engine code.

Gas cap costs around $15. Unlikely that's the cause.