my stupid check engine light came on last night so i made an appointment for next week to get it checked out. yes, i checked the fuel cap, it's fine.

anyway, i know there's nothing too terribly wrong with the car unless the light is flashing but i was just wondering: what sort of things cause the light to come on anyway?

the check engine light is a bit of a mystery to most drivers on the road. it's a light that doesn't mean a hellova lot to those with warranties, it can be a complete stress causer to those that know nothing about it or cars, and for those with old cars, it means nothing at all. most owners of old cars are accustomed to just driving around all the time with the stupid thing lit up.

anyway, what sorts of things on an MB cause that worthless light to light up anyway (besides the fuel cap being loose)?

 

Get a scanner or scanner software for your laptop and the mystery is solved. I got mine at www.obd-2.com for about $120. 20% off with a student discount.

 

Or just swing by your local Auto Zone-they'll let you use their OBDII free of charge-you just have to be able to figure out the code it gives you.

 

It's usually just a fuel system problem that fixes itself or a misfire that happened, but does not indicate a problem. If it runs fine, it usually is fine, it just needs to have the light reset.

 

i'm sure that's it. there's nothing wrong with the car. i'm not worried about it at all, i was just curious as to what sorts of things tend to cause that light to light up in an MB.

aside from the annoyance of the light being on, i couldn't care less. well, that and the fact that i have to take it in to the dealership to be reset.

 

one of your oxygen sensors could have gone bad, that will sound the check engine light

 

Ah, the first few problems encountered with the C Coupe. I once thought "there's nothing wrong with the car"...

7 trips to the shop later, I now know I was wrong.

 

as long as i don't have to pay for any of it. that's what warranties are for.

 

You still pay in the cost of time. My time is worth a lot to me. However, I still enjoy my car.

 

My car is in the shop now for the exact issue "check engine light" The mech said it has a faulty "engine controller" and need MB aprroval to replace it with part that will be shiped directly from MB using the specific VIN. SOund like big bucks to me.

Anway it was in last wed and i was promissed Monday completion.

I'll let you know the proper tech term and part number to this solution.

This is definitely more serious than the "gas cap" answer. I am told to hang on to the loaner for the duration because the Coupe is liable to stall-out at anytimes and it would be real bad if it did on the highway.

More to come.

 

Benzer, there are many things that can cause the check engine light to come on. The fix for yours is not necessarily the fix for truelove's car.

 

The thing that few people consider in a newer car is that not only can the warning light be triggered by one of the components that it monitors. These known fault codes are no doubt exhaustively covered off in the workshop documentation. So far you need a Captain Benzo Secret Decoder Ring and have to know the Secret Handshake to have access to this info. I digress. Unexpected (and undocumented) wiring problems can also give rise to check engine lights, and these are usually caused by connector corrosion or bad grounds.

I would imagine some of the "normal" codes would be for:
- air flow sensor malfunction
- throttle position sensor malfunction
- electronic throttle actuator malfunction
- rpm (tdc) sensor malfunction
- detonation sensor malfunction
- various temperature sensor malfunctions
- ECU malfunction
- fuel pressure malfunction (pump pressure too low or high)
- injector malfunction
- low voltage (or high voltage)
- ignition system malfunction
- supercharger malfunction (??)
- oxygen sensor malfunction
- catalytic converter overheating
-ad nauseum

An undocumented wiring problem was certainly the cause of the infamous BAS/ESP error that afflicted so many W 203 cars.

And therein lies the problem with motor vehicles that are excessively reliant on electronics. In real world usage, cars are exposed to all sorts of nasty environmental conditions, and these can cause wiring looms - their connectors in particular - to become crap after several years. Airlines are discovering this too, the wiring in many modern aircraft often becomes dangerous after a decade or so. The insulation in particular breaks down. This has caused many air disasters.

Time to be a low-level Luddite . Give me Kugelfischer mechanical fuel injection - like my 404 C has - any day. 100% reliable, better looking than electronic injection systems and - I think, a more elegant engineering solution. However, KF injection will not get you EU-4 emissions certification (or even EU-1 for that matter) and besides they've been out of business for 20 years....

 

well, the problem must not have been too serious. the light is not on anymore. must have been bad data logged from one of the sensors or something and is no longer an issue.

i work for a department in Caterpillar that tests powertrain, implement and engine control and i know how complicated electronic diagnostics and controllers can be. with such complicated systems, a simple logged error not only doesn't surprise me, but doesn't worry me or upset me in any way.

i'm sure component errors and simple problems have always been an issue even with older "reliable" cars. now the car is just smart enough to be able to detect and report these errors, while in an older car, we would just keep on driving never knowing these little things crop up.