Check Engine Light on C230
 

I was wondering if anyone knows how to see what the problem is on a 1998 C230 when the check engine light comes on. I really don't want to hook it up to the diagnostic machine the dealer has I would much rather find out myself.

The possibilities are huge without having the codes read. Why not do that? With OBDII mnay shops can read the codes for you. It would save you tons of diagnostic frustration.

It could be a misfire from a fouled plug, bad resistor, or other thing.

It could be an O2 sensor

It could be the MAS

Tranny problems trigger the CE light too

And on and on...

Thanks for the response. To hook the car up to the diagnostic machine the shop has is expensive and I was simply trying to save a couple dollars. But I think that may just be the only way to see what is really going on.

Hey Nate,

Right after my 75k service, I had the same thing happen on my 97 C230. Without an expert diagnosis by reading and interperting the codes, you'd be guessing what the problem is.

My independent shop pulled the codes and replaced the MAS. I was bummed that the part was not covered on my warranty but happy that the problem went away.

My understanding of the issue is that it's incredibly common and basically nothing to worry about. That particular part is basically a "wear" item that gives up after a while.

Good luck,

In a discussion of air mass meter failures (I presume that is what MAS is refering as I don't think any C cars had MASs) I read recently it was pointed out that the reasons for these failures is often a aircleaner situation. Slight leaks or lack of maintenance causes a dirt layer to insulate the film used on the new hot film mass meters. The hot wire systems in previous LH systems were more durable because they had less surface area to foul and they had a burn-off function after shut-off. (The wire was taken red hot for an instance to clean it)

Some manufactures are actually going back to the hot wire burn off set-up just for that reason..

Some time ago I had another tech mention that engine-air filter replacement frequency was related to AMM failure. I have been replacing the air filter element and cleaning the intake air filter housing and ensuring it's sealed at every other oil change. This may seem extreme, but the filter element take two minutes to change and is only about $20.

So far, no problems. (Touching wood)

Steve, I'm wondering about terminology. The dealer refers to theat part in my C230 as a "Mass Airflow Sensor" but you explain that MAS and Air-Mass-Meter are different things. I am curious as to how they are different. Both units seem to use a hot-film set up that is lacking durability, unfortunately.

The terminology problem is that the acronym MAS is already used for a different device. The original MAS is a voltage supply relay that combined the OVP, the FP, and Klima relays with a couple new functions in about 1990 300Es.

There is only one air mass meter/mass air flow sensor/air flow meter. The first term describes the device so I prefer it. To change it to Mass Air Sensor doesn't bother me, but if I didn't know what it was the name wouldn't tell me. After all, what is mass air. Air mass is defined by the words. The actual name was complicated by the fact that early devices were just air volume meters. They moved a door for sensing. The newer devices do better than just volume by finding mass. Volume times weight equals mass (or some such). Early sustems figured all air had the same weight. That worked for pre lambda cars.

The LH -SFI and HFM-SFI systems are both Full Electronic measure of air mass without any mechanical to electric sensing ..
[ mechanical vane or flap mechanically hooked to a pot resistor ]
These are called MAF [ mass air flow ] sensors.
They work by maintaining a temperature through a weatstone bridge circuit and the reguired voltage to maintain this temp
is analized by the computer .. kind of it's own little closed loop maintaining system,,-- so, no Mechanics of any kind ... and a better sensor, as it considers air density/temp now..
LH uses a Hot Wire to do this, and the later uses a Hot Film .. otherwise , they are about the same ..
The new technology on air measure is AMMs that use a frequency base signal, rather than linear voltage,,
I think we will see these in every car in the near future, along with Wide Band 02 sensors
...they just get better and better ,,,

Using MAS for MAF , or AMM can be confusing , but when in context, I think we know what is referred...

I also have the same problem. The check engine light on my '97 C230 (73k mi) came on tonight but I believe I have fixed the problem. Is there any way to turn off the dash light without going to a shop?

i know this works but could a TECH verify if its a good idea. You can disconnect your battery for a few mins and then reconnect it, just take off the black wire. This resets the computer and the engine light, if everything is fine then it shouldnt come back on. I have done this with much success.

Removing the battery does clear engine codes. It won't clear many others like SRS. As the cars get newer the problems caused by disconnecting the battery can get gruesome.

I had a 2001 E320 brought from a bodyshop 50 miles away because they accidentally turned the key on while the rear door panel (and door airbag) were removed. He thought he would try the battery trick. It didn't help his problem and he lost the initialization of the throttle, the windows, the sun roof, the seats, the steering angle sensor (which set the ESP/BAS lights) and he lost the proper configuration of the D2B optical network. It would have been a real mess if it had been an "S".

Problem Fixed
 

Thanks everyone it turned out to be the MAS sensor. Every since I replaced it the light hasn't come on.