My 1994 E320 wagon recently provided that chilling "check engine" message that is most disturbing to one's financial well being. After a visit to the local dealership, the diagnosis was-failing smog pump and computer. After opting for the $900 smog pump replacement and passing on the $1700 computer replacement, the car ran just fine (same as before the pump replacement). After about three weeks, the dreaded "check engine" light was once again illuminated. The car still runs great, but I am concerned. Is continuing to ignore this message a catastrophe waiting to happen, or a nuisance provided by a conservative manufacturer? Can the "check engine" light be reset without going to the dealership? Is this computer replacement even a credible diagnosis? Any suggestions?

Sorry to hear of your "loss" of $900 for the smog pump but look at it on the bright side, you will not have to worry about it for another 100k miles. It is my opinion that you need your line from the egr valve to the intake manifold "rodded" out. Takes me about 1 an hour using a section of an old speedometer cable - the cable is the "rod". Not too hard to do for a compentent diy'er.
good luck

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Jim

Thanks for the reply, I will give it a shot. How about the "check engine" light that is driving my wife nuts? Any DIY reset procedures available?

The check engine light will go out after x number of "cycles" after you resolve the issue with whatever is turning it on OR you can disconnect the battery for a few minutes and turn the light off temporarily. The light will stay off once the problem is resolved. Try rodding the egr port first if it is giving you egr "inoperative" code.

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Jim

Thanks again.....

Unplug the batter for a few moments.... Check Engine light will reset.

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2006 E350 w/ 155k miles (Daily Driver)

Previous:
1993 300E 3.2L Sedan w/ close to about 300k miles
2003 E500 Brilliant Silver (Had 217k miles when totalled!)
1989 300E with 289,000 miles (had for <1 yr while in HI)
03 CLK 500 cabrio (Mom's)
2006 C230k (Dad's)
1999 S420 (Mom's/Dad's)
2000 C230k Sport sedans
2001 CLK320 Cabrio (Mom's)
1995 C280 My First Mercedes-Benz... (155k miles. EXCEPTIONAL AUTOMOBILE. Was Very hard to let go of!)

I tried disconnecting the battery for approximately 60 seconds, but the light was back on right away. Was this a long enough attempt? Also, there is a strong odor of gasoline at the exhaust pipe for the first few minutes after a cold start? Part of the same problem?

THe code probably cleared... but came back on right away because the problem triggered the computer to turn on the MIL again.
you can try unplugging it for about 10 minutes...?

You'll have to get the code read... and find out exactly what the code is telling you!

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2006 E350 w/ 155k miles (Daily Driver)

Previous:
1993 300E 3.2L Sedan w/ close to about 300k miles
2003 E500 Brilliant Silver (Had 217k miles when totalled!)
1989 300E with 289,000 miles (had for <1 yr while in HI)
03 CLK 500 cabrio (Mom's)
2006 C230k (Dad's)
1999 S420 (Mom's/Dad's)
2000 C230k Sport sedans
2001 CLK320 Cabrio (Mom's)
1995 C280 My First Mercedes-Benz... (155k miles. EXCEPTIONAL AUTOMOBILE. Was Very hard to let go of!)

Thanks, I will try a longer cycle. What do you think of a diagnosis that suggests replacing the engine computer to resolve the problem? My understanding was that the engine management system either operated or didn't, but not partially. Your thoughts?

Wasn't this year when they had problems with the wire harness?
Just a suggestion!

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J.H.
'86 300E

I too have the same trouble with my 94 e320 sedan. I have an extremely knowledgeable tech that went over the car before I purchased it.

Apparently this is a common problem in this car. The cause is usually associated with the EGR valve, wiring harnes, and or computer.

The EGR valve in my car has been replaced and I still have problems with the light. The wiring harness and computer are both big expenses. I've been told that I should not worry about the light.

Unfortunately, not worrying about the light is not something I can do. If you find a fix, please let me know.