Check Engine Light
Anyone ever had this happen?
Anyone ever had this happen?

variety of reasons. the hundreds of sensors aid in providing feedback to the
many interrogation systems, one of which monitors for CEL alerts. some of the
triggers may be transient and disappear. the CEL may log the error code but
not light up as it views the error as a 'false positive.' if an error code repeats
then the CEL lights up. if, within a relatively short time, the code vanishes,
so does the CEL.
OBDII code readers can be had for as little as $25 or so. It would be similar to
owning a volt meter, ie always good to have one if you're the type of owner
who likes to understand why something is happening to your car vs someone
who would rather turn the car over to a dealer to perform the diagnosis




there are no hundreds of sensors to set the CEL.
The car has Mass Air Flow Sensor(s), Intake Air Temperature sensor(s), Intake Manifold Pressure sensor(s), Crank Shaft Position sensor, Cam Shaft Position sensor, and Oxygen sensors before and after each catalytic converter in the tail pipe. In a car like ours with dual tail pipes and catalytic converters and dual intakes it means 12 sensors max. I don't think they use two sensors for temperature so it probably is just 11 and if they don't use Mass Air Flow sensors it brings it down to 9 sensors. Some cars use fuel tank pressure too so this could bring the number of sensors up by one. In any case there are no hundreds or even tens of sensors.
CEL is an indication for emission control system not working properly. The OP says he got the CEL after a short distance of driving. The key here is how short. From cold temperature start it can take quite long drive before the fuel control system goes to closed loop control as the catalytic converters must heat up to working temperature. This means that the CEL will not be triggered by the normal emission sensors right after start. What can trigger it very quickly is misfire (no specific sensor) or the crank shaft / cam shaft positio0n sensors. All of these can be triggered by moisture for example.
The OP should read the saved code. The light went out but there should be a saved code to read of what set the light.
Some auto part stores like AutoZone read codes for free. They will not reset it and good so as it will be for MB to read too.
Last edited by Arrie; Jan 11, 2015 at 11:43 PM.
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Anyone ever had this happen?

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knowing the code would be a big help to, get a cost estimate, and make sure they don't try to tell you
something is wrong that isn't
an OBII tool is great to have....although I don't have one either




"CEL comes on for a
variety of reasons. the hundreds of sensors aid in providing feedback to the
many interrogation systems, one of which monitors for CEL alerts."
How should I understand this?




DAS STAR TEK or other high end devices read all sort of codes beyond the ones that set the CEL. This is how I understand it.
Different states probably have different rules for this too at inspection. When the CEL is lit in my state they scan the car and if there is only one code that set the light the car will pass. Two or more codes it will not.
For folks wondering what help the OBD II scanner is some very easy fixes include gas cap and oxygen sensors. Oxygen sensors are one of the most common problems and in general are very easy to change. This, of course, if the car is outside warranty. Gas cap is no brainer.
When it gets to crank shaft and cam shaft position sensorss I have no idea yet how to do it on the E but have changed these before on another vehicle.
Just bought my OBD II scanner for $130 from AutoZone. Have not needed it yet but plan on using it at the first sign of any issues.
Last edited by Arrie; Jan 18, 2015 at 02:53 PM.
You can use an inexpensive scanner to read the ECM, of course the mfg will have the ability to read and program to much further depth.
Anyway until or if it happens again I'm not going to worry about it.






