98 ML320 54000 MilesCEL

[Vinnie1068]

Hey you guys could you PLEASE HELP? Gilly if your out there please answer.
IS there anyway to reset the CEL without actually disconnecting the battery to force the system to reset the light? I am chaning out the MAS because of all syptoms poinnt to this but what if that doesn't make the CEL light go off is there a way to reset the CEL light? The guys at Auto Zone said that they used to reset the light by disconnecting the negative paower to the battery for twenty minutes, is this the only way to accomplish it? Thanks in advance for your help. Vince

[jfinch]

The guys at Autozone should have a code reader that you can use to pull the codes. Then you will know what is causeing the light to come on. It might be your MAS but it might not be that either. The code reader can then be used to erase the codes and turn the light off.

[Gilly]

I agree, if they can read the codes, they should be able to delete them.
I wouldn't recommend trying to clear the code in this manner anyways, you lose transmission and ring gear adaptations.

Gilly

[Vinnie1068]

So if they were able to read them with their nifty little code reader then this reader should also be able to delete or erase the codes? Is that correct? What if I change the parts out and let the codes remain will the light go out on it's own assuming that I corrected the problem? From everything I have read so far here and elsewhere what I am getting is that it takes some time to actually have the computer remove the codes. Is that true or will it remove the CEL and codes on it's own fairly quickly? Once again assuming everything is corrected.

[mbdoc]

On MB's after 1996 the computer will "erase" the code after the problem is fixed! May happen after a few starts or possibly take several weeks to re-set!
The criteria is different for different codes/problems!

Posting the code number that they read would help

[Vinnie1068]

Thanks the codes were P0170 & p0173 when read by Autozone.

[mbdoc]

If you replace the air mass sensor & drive the car that check engine will reset
if that was the problem!

[Gilly]

Agreed.
Yes, there reader should be able to reset the code, but if you don't feel like going back, it should go out on it's own, may take a few days. Hopefully there weren't additional codes they didn't tell you about which is making the light remain on.

Gilly

[jfinch]

It varies how they handle the code readers. At AutoZone they said they were not allowed to clear codes but he handed me the reader and I did it while he looked the other way. They were using an off the shelf Actron unit you can buy in their store. At the local Advance they had a special unit also an Actron. He gave me the unit, proper adapter and I had to hook it up and follow the instructions so it could read the codes. It would not display them though. I had to take it back in the store and they hooked it up to a printer and gave me a print out of what the codes were. I then went back out and cleared the code and returned the unit.

[Vinnie1068]

Well guys just as you all stated and in similar posts off the site, the CEL light went off after replacing the MAS, Mass Airflow Senor! Hurray! I found one on the web for $168.00 original MB part still in the box, got out my handy dandy screwdriver loosened the clamp, unsnapped the the snap switched it out and evrything is fine. It took a day and half for the actual CEL light to go out just as Gilly and and MB man said so I am guessing that the MAS was in fact the problem abd not hte O2 sensors as the OBD II said it was. I actually noticed some improvements in performance also that I should mention like the idle speed is greatly improved I mean it doesn't jump up and down when idling at a light with the AC running near as much, it seems to have gained some control back, the shifting also seems improved I mean the down shift from 2-1 when nearing a stop, and overall pep has improved to a great extent. One more thing I noticed is that the gas mileage seems to have also improved, that is by the on board estimates of the trip computer they are much higher without changing the way that I drive. On average it seems to have added 2-3 mile per gallon of gas, not major but at todays prices in Houston, TX that is signifcant. A fill up with Premium is running between $35.00 - $40.00 with a quarter of a tank left. Thanks to all who have helped me on this matter couldn't have done it without you guys. You all are fabulous!

[Gilly]

Good to hear Vinnie, also wondering if the plugs have been replaced? That'll help performance and economy too. A 98 is past due, even with 54K on the odo.

Gilly