hi guys, the "check engine" light just came on in my '94 E320, can someone direct me to the link on how diagnose this? thanks......

 

Depending on what part house AKA Auto Parts Store you go to, you can get it diagnosed for free. I believe O'Reilly, Autozone and Advance all diagnose for free. They hook it up to a machine and it will give you and idea of what might be wrong.

 

None of those stores will do it since it's a 95. I'm not sure if your car has the 16-plug diagnostic connector, only cali cars have it. But just incase:

Reading Fault Codes

- Turn ignition key to “on” position, all dash warning lights will be on.

- Remove cover on 16 plug diagnostic connector near battery.

- To read check engine light codes (DM), hold down built in button next to LED light for 3 to 4 seconds, LED light should be on, release button, count the number of LED flashes that follows. Hold button down for 3 to 4 seconds again to check for another code. Keep doing this until all codes have been read and first code comes up again.

- To clear codes - hold down button for 10 to 12 seconds, turn ignition key off for a few seconds, repeat to clear additional codes. Ignition must be turned off between each code cleared.

To check other modules using code tester – insert black plug into socket #1 (ground). Insert red plug into socket #16 (12V power). Insert yellow (third color) plug into socket to be tested, for example #8 or #14. Repeat steps above for LED button using code tester button and LED. Same process for deleting codes as with LED button.

Check appropriate fault code list to determine fault.

Checks codes as quickly as possible at the first sign of a problem. Codes spread from one module to another and will often show up twice or cause other codes. The sooner you check the codes the more likely you are to identify the source problem.

 

Your car is pre-OBD2, and has on-board diagnostics that are relatively easy to access... easier that OBD2.

These two links should have all the information you need to make the code reader, use it, and interpret the codes. It covers what battlecat wrote, plus some.

http://www.mercedesshop.com/shopforu...d.php?t=107630

http://www.geocities.com/MotorCity/D.../cs1000_mb.pdf

Read through the info, then post back if you need clarification on anything.

 

Highly suspect the egr valve or the hot inlet tube that usually cakes itself clogged over the years. That can trigger the CEL.

 

Many thanks to all. I tried resetting the CEL without reading codes by disconnecting the (-) batt cable for a few minutes, light went out, but came on again next day. Guess I got to do it the proper way. I'll post any relevant information or problems with the code readings.

 

hey guys, I can't seem to find the built in button or the LED light next to the 16 plug diagnostic connector. attached is a photo of the 16 plug connector with the cover off next to the battery. would appreciate help in locating the button and light. the car is a '94 e320. thanks........................

 

seems the photo didn't attach itself, gotta figure out how to get pic into post........

 

The No. 2 position is the button. Turn the ignition on and press the button down 2-4 seconds and see what happens.

 

thanks kestas for the quick reply, there is no button or LED light on the connector block, what do you mean by #2 position?

 

just went out to the car to look again, found the button and light by #2 connector, it was covered by 1/4 inch of crud, thanks Kestas very much! I hope the CEL isn't a serious problem. it seems to come on ONLY on an engine startup. it never comes on while engine is running. I been disconnecting the (-) battery terminal to turn off the light on a temp basis.....

 

Kestas, I ran the pulse diagnostic, it came back with 3 pulses, which is the "coolant temperature sensor". is it one of the three connectors on the thermostat housing? also, I clear the fault codes yesterday and the CEL hasn't come back on yet, usually comes on when I start the engine. thanks for your help..............

 

Was the code from the built-in diagnostic unit (Button 2), or from Pin 8 or 14? Which chart did you use to interpret the code?

If it's from the built-in diagnostic unit, Code 3 means "Lambda control faulty".

Make yourself a code reader and get the codes from Pin 8 and Pin 14. This may help determine what is going on. Once you read the codes, erase them, then reread what comes up a few days later. It's not unusual to get spurious codes from engine hiccups.

 

Kestas, the reading was from button 2, the chart to interpet the 3 pulses came from: http://www.mercedesshop.com/shopforu...9&postcount=13
it's been 2 days now and the CEL hasn't come back on, the dash temp guage reads normal, the radiator fan seems to kick on properly. wrong interpetation of code? what's a lambda control? again, thanks much for your help.......

 

The chart is for an 88-89 model benz. I think that is where the discrepancy lies.

Read through the information I linked for you in Post #4. This should bring you up to speed on your model. Make the code reader* and read the second level of codes. This should give more detail.

Lambda control is another term for air/fuel mixture control. Lambda can affected by the O2 sensor and air mass meter. A simple no-cost thing you can do is clean the air mass meter sensing element with contact cleaner or alcohol. But you have to be careful because the sensing element is very fragile. Hopefully you're not using a K&N filter!

(*) - Or use the multimeter method, which will give the same result. In my opinion the home made code reader is more convenient.

 

Thanks Kestas