markjenn

Is there a fuse you can pull that will reset the CEL or do you have to disconnect the battery?

Thanks,

- Mark (2000 ML320)

GDawgC220

you can disconnect the battery for a few minutes and plug it back in. that should take care of it.

any idea why your CEL came on?

mihir_d

I thought, one could reset the CEL with the help of an OBD reader..

GDawgC220

yes, you can use that as well. But if one doesn't have that tool, the battery would be the easiest way to reset it.

markjenn

I don't know why I'm getting the CEL, but I want to do a reset and see if it returns before takiing it in.

- Mark

mihir_d

If that is what your line of thought is..to always DIY before taking it in, invest in a OBD reader...it will tell you what the codes are set on your car's computer...

ML God

Sorry, you cant turn the light off by disconnecting the battery, It has to be done with a scan tool or by your dealer

GDawgC220

really? I've tried it with my w202 and it worked. But it did come back on a few days later, indicating that there was an actual problem. But I assume you can do it on all the cars cuz it resets the computer (including clock, radio, adaptive tranny settings, etc)? Interesting...

ML320AMG

the CEL fault codes does go away with the batt d/c method. But the ECU checks the circuit on the car the second you start it ... if the part is faulty .. it'll come back to haunt you.

For Markjenn i can scan it for you if you are in Los Angeles area. if not you can try to call your local autozone and see if they still do it for free. I know most of the CA stores stopped doing it because the labor union filed complaint on them for giving this "service"

DIYwannabe

Autozone checked and reset mine last week in GA for free. It worked out perfectly. I had done some repairs and apparently set of an O2 sensor. The code reader (that the autozone guy said they sold for $149.00) worked great. It showed the code with short explanation - i.e. O2 sensor malfunction, bank 2, sensor 1 (Exactly where the work was performed). He reset it for me and I've since put 500 miles on the truck with no more check engine light warnings.

markjenn

To close on this, I took it to a local garage and they read the code: failed O2 sensor heater. Apparantly, the O2 sensors have electrical heaters to get them to temp quicker for emissions reasons. Only fix is to replace the sensor - about $175+labor. I was hoping for coverage under the 80K emissions warranty, but MB says O2 sensors aren't covered.

- Mark

mihir_d

O2 sensors should be covered since they critically affect emissions...and anything that critically affects emissions is covered under the emissions warranty...

markjenn

That's what I thought, but the warranty does not say they'll warrant all emissions-related components for 80K. It says they'll warrant everything for 2-yrs/24K but only certain components for 8-yrs/80K. The things that are subject to the longer warranty are actually quite limited: cats, engine computer, the CEL lamp, and a catch-all for hoses, clamps, etc.

Obviously the 2/24 warranty is largely redundant since the entire truck is warranted for 4/48.

Page 28 of the "Service and Warranty Information" book has the grim details.

- Mark

mihir_d

2/24 covers all components that affect the performance of the exhaust system...

8/80 covers all components that affect the emissions of the exhaust system...

Its then similar to the Mass Air Flow Sensor (MAF)...the MAF is also covered only for 2/24 like the O2 sensors..

The MAF by the way senses O2 content prior to iginition..the O2 sensors sense O2 after combustion...both could effect emissions, but I guess not as critically as something like the CATs...that's why they are not covered..

$176+labor is not bad for the O2...considering $350+labor for the MAF...