Update - wiring harness has been replaced, but...
 

An update on the check engine wiring harness on my 1993 300E 3.2. I took my car to the dealer to plead my case on a 'goodwill repair'. Before they committed to helping my out or showing my the door, they checked to see the condition of the engine wiring harness. They checked the number on it and to prove it to me they even sliced open a portion of the black fabric covering on a section next to the firewell, and lo and behold, it has already been replaced.
I guess this is good news, but the bad news is WHY IN THE WORLD DOES MY CHECK ENGINE LIGHT ALWAYS COME ON!!!
The code '5' always comes up, which is an oxygen sensor. The car has a new catalytic coverter and oxygen sensor (changed twice). The mechanic suggested that if the car was running rich it might cause the code to come up. They checked it out while I waited and said it wasn't running rich. He couldn't find any good reason why the light comes on.
The mechanic then loudly proclaimed in a load voice so that everyone within earshot could here, "this car doesn't need a mechanic, it needs an excorsism!" Everybody laughed and I felt like Charlie Brown. You know, like when they go trick or treating, and everyone says what they got, like "I got an apple, I got a candy bar", and Charlie Brown says, "I got a rock..".
As I've said before, I've taken the bulb out so that I don't have to see the check engine light mocking me. But it gripes me to no end that I can't figure out. I know I'm not only anal retentive but also obsessive compulsive.
Does anybody have any suggestions????? Oh, where's the humanity?

You are looking at the EGR code, I believe.
This EGR code is a common fault on 104 eng . Search archives for S.B's article on the EGR tube plugging up at the intake feed port of the head.
There is also a part change modification.
Simple test for port clog is to apply vac to egr servo at idle . Shoud run rough if port is clear. No change indicates egr/plug tube diagnoses.

The photo and link is at the end of Steve's article at http://www.peachparts.com/Wikka/EngineControls :)

#26 code?
 

Thanks for the reply.

I also got a #26 code. Any idea what this means?

thanks. Paul S.

Shift delay switch-over vale.

The tranny delay shift control when the car is cold.
Over by the master brake cyl. Black switch with 2 wire plug and green vac lne.

May be unplugged.

Progress on Check Engine light problem
 

I finally found the time (and the courage) to check on the two possible solutions to my check engine light problems. I used to do all the work on my cars when I was in high school and college and had no money, but I've gotten kind of lazy over the years...

The #5 fault code is an EGR valve problem. I had already replaced this, but since the code came up again, I was blaming the light on the wiring harness, but this had already been replaced. Since I had nothing else to blame on this problem I knew I had to find a solution, expecially since I've thrown about $2,000 at this problem.

Thanks to Arthur Dalton's suggestions, I checked out Steve's article, and he commented on a similar problem on a C280. The problem was the hot pipe inlet to the intake manifold was carboned up from PCV (partial crankcase ventilation) vapors. To test, I applied vacum at idle, and the engine idled perfectly, suggesting the port is plugged up. This test took about 30 seconds to perform. I can't believe both the dealer and two independent mechanics missed this.

Regarding the #26 code, I located the shift delay valve next to the master cylinder. It has a black plug with a green wire and black wire leading away from it. I pulled off the green line, blew in and out on it, and sure enough, it is plugged. I dropped off the car at my mechanics last night who charged me a good deal of money to fix the car, and didn't. Needless to say, he's performing this for free! After all, I explained to him that he should be paying me as a consultant for his ongoing education. :D :eek: :)

Congrats and finding the info to be of help and thanks for the note of appreciation. [ in behalf of all]
This forum can and has saved Benz owners thousands of $$$$$$$ and is an asset to all !

Just an update on the repair.

I got the car back from the mechanic, and he performed the cleaning procedure on the hot inlet pipe to the intake manifold. It actually was pcv vapors leaving behind carbon that plugged up the pipe.

When I got the car back home in the garage, I unplugged the green vacuum line. Sprayed some brake cleaner in there and blew the heck out of it with my air hose. It's a very small diameter hose and hard to clean it out. When I blasted it with the air hose, brake cleaner sprayed everywhere and the hose flew out of my hand across the garage floor.

I then pulled the plastic off the gauge cluster and had a terrible time trying to put the bulb for the check engine light back on. Must have spend 2 hours. I finally used some tongs from the kitchen, like the kind you use when your frying chicken, and put on disposable rubber gloves over the end of the tongs - like the kind your proctologist uses when he says "bend over and grab the table!".

My only regret is that I kind of put some minor scratches to the black trim around the ac vent to the right of the gauge cluster.

I touched it up with a black sharpee pen and it basically covered up the scratches.

It's been a whole week and the light hasn't come back on yet!

I find myself continually staring at the check engine light, though, waiting for it to come on while I'm driving, and I'm afraid I'm going to rear-end someone driving back and forth to work!

lol - you must be relieved though that the repairs were relatively minor. There is nothing worse than having a non impacting fault that you can see all the time.

Matt.

Update of check engine light
 

The check engine light came back on yesterday.

Even after I addressed both problems, the d*** light came back on.

Oh, Lord, please have mercy on my poor soul.

I think I'll start a poll. It may go something like this:

Paul has a check engine light that won't stop coming on. After spending over $2,000 hand over fist to prevent one stupid emissions related idiot light from coming on, he should now:

A. Take a sledge hammer and beat the car.
B. Take a sledge hammer and beat himself over the head.
C. Go ahead and remove the idiot light one more time and pretend like it's not even on.
D. Take it to the dealer and see what they say.

I don't know what codes popped up this time. I'm going to wait a week or so to allow me some time to regain my composure.

I really don't know if I should continue to throw money at this problem. Both independent mechanics say there is nothing wrong with the car, no reason for the light to come on. They think that there are some MB's where the light comes on inexplicably. My pefectionist / anal retentive / obsessive compulsive nature tells my this is a cop-out.

Any ideas?????

Paul,

Sorry I don't have any additional ideas beyond what you've tried. I just wanted to add that you won't be able to pass your next smog test with the bulb out or with the light on. I don't think you have a choice other than to keep on pursuing it.

Has anyone stuck an old fashioned sniffer in the tailpipe to see if there are any emissions measurements obviously out of spec?

I recommend you just pull the codes . Your car has the led/sw diagnostic box, so it does not have to go to the dealer to get them.
I can see your frustration, but remember there are 28 different emmision related codes that will trip that CE lamp, so you may have a completely different code than previous problems.
Post us what you come up with for codes.

The continuing saga of the Check Engine Light
 

By searching the discussion forum, I learned that by pressing the button for 3 seconds (with the engine off and the ignition in the on position) and releasing, you count the number of flashes for the fault code.

I got 26 flashes, which would be the same code as last time, the upshift delay valve.

I determined that the green vacuum line was plugged, so I unplugged it, and replaced the switch (a $30.00 part).

Why would the code come back on?

I know that the upshift delay valve is working because it does keep my transmission from shifting into high gear when cold.

The only thing I can come up with is possibly the switch is not getting enough vacuum to work.

Does this make any sense?

I then cleared the code by pressing the button for 8 seconds and then releasing. The Check Engine light is now off.

I just wanted to memorialize for posterity that it is now March 19, and the check engine light hasn't come back on.

My only conjecture on why the fault code came back on for a faulty transmission up shift delay valve after replacing the part is that the fault code was still stored in memory from before the repair.

In any event, I consider case closed on all check engine light problems (knocking on wood).

Persistence and a logical mind has cured more ills than impatience and frustration. Congratulations!!!

Your vehicle has been exorcised!:D :D :D

My car has been blessed by both a Priest and a Rabbi (just in case). lol :eek: :D

Paul,

It certainly sounds like your persistence and exorcism has been successful. I need to find the formula to exorcise mine!!!

My question to you is: has your gas mileage been affected by all these events? My headache is not too different from yours, but my mileage is down about 25%.

Mine is a 93 300E 2.8. A slightly different engine. Just before 95k mi. the CE light came on -- O2 sensor bad. I replaced it with a Bosch generic unit (after calling Bosch to make sure it was the right one -- 4 wire interface). In a couple of thousand mi., the CE light came back and would not go off. This time, to a dealer, who said the wiring harness was shot. The dealer replaced it at no cost. Since that day, the gas mileage has gone from about 25 mpg to 20. That has really has bothered me.

A few days later, the CE light came on again. The dealer said its the O2 sensor -- running too rich. This time, I had it replaced with an OEM O2 sensor. A little while later, another CE light -- this time, the EGR code. Got it fixed. Next time, the intake manifold length tuning flap. Got it replaced. None of these has brought the mileage back up. Now, it's giving the 26 code. After reading your thread, I'll check the vacuum on the tranny delay shift switch (and the switch). That should remove the 26 code, but won't account for the gas mileage drop.

Any ideas on what might cause the reduction in gas mileage on this car that runs perfectly -- now with 134k miles?

Thanks,

With all the O2 sensor and egr codes, you may have a plugged hot inlet pipe to the intake manifold. The egr valve is on the exhaust manifold, and when the egr valve opens, it allows egr vapors to travel back to the intake manifold via this hot inlet pipe.

Steve Brotherton wrote an article in the DIY link at the top of the screen called Evaluating Electronic Engine Controls that shows this problem on a C280, which I think is the same engine as yours. The first half or so of this article is too technical for this shadetree mechanic, but this problem is explained at the end, with pictures. This condition seems to be systematic with all M104 engines (including mine).

This pipe gets coked up with carbon from these vapors, and triggers a code for low egr flow.

The fix is to ream out the pipe with a cable, like a speedometer cable, and a drill motor.

I've think I've read a post from Benzmac saying that he performs this every 30,000 miles on M104 engines as part of regular maintenance.

My mileage didn't really suffer through this process, only to the extent that it dropped while the mechanics kept the engine running so long diagnosing it.

My average mpg is about 21 - 21.5 consistently.

I have experienced in other cars significant drops in mpg when my O2 sensors were bad, though.

Don't give up on your problems, though. I had one indie mechanic give up and say he couldn't diagnose my CE light problems. Another indie mechanic blamed it on the car , you know "..sometimes these engines have CE light problems that have no real source...yada yada yada yada". He was wrong, and this website helped me diagnose the problem.

Paul,

Thanks for the suggestion on the hot inlet pipe. I'll have this checked out when I bring my car in for the next service next week.

I've not given up on bringing my gas mileage back up. I've seen a number of mechanics, including at Fletcher Jones Mercedes, regard a constant CE light as just normal on an old 124. But I have the same compulsiveness you noted in your earlier posts. Fixing a problem like this just takes time and patience, which is tough. But I know that, eventually, I will prevail. BTW, I've also found the help on this forum to be excellent.

You're in Mission Viejo. I just came back from the Cheesecake Factory at the Mission Viejo Mall for a get together with my brother's family.

JCE (John) lives just across the freeway in San Juan Capistrano.

We had our last get together at the mall, where we looked at our cars, shared experiences on repairs, maintenance, upgrades, etc.

You should come to the next one.

John knows a great Mercedes independent mechanic in the area. You might e-mail him through the site to find out who it is.

Paul,

I'd be happy to come to the next meeting. John and I have talked about meeting, but never got it together to do so. Keep me posted.

I know of his mechanic, but it's not close for me since I work in Irvine. I have a fine mechanic in Newport Beach who does most of the work on my car.

By the way, fwiw, you may have noticed that Arthur Dalton helped me a lot on this thread, and I've noticed he helps a lot of people with CE light problems.

He seems to know enough about these cars, that I'm willing to bet he either is or was a mechanic on these cars.

He also knows what each code number means for each car.

He may be able to provide insight / support for you, as well.

I also recommend you do what I did. I print out pages from this website when there's been a diagonsis that matches my problem and show it to my mechanic. He may be a little insulted, but it's your car, isn't it?

just some more feedback on those pesky "upshift delay" problems.

simple check out for function, unplug the hose leading to the bowden cable from the upshift delay swwitchover valve and apply a hand vacum of 20 hg or so, drive it, it should sift under very light throttle at 2400 or so for most 103's and 104's, if it dont, adjust the cable. Its the 5mm hex on the backside of the upshift delay actuator on the r'h side of the tranny. Not all models have 1-2 delay such as the 202.028 (c280, 1995), check the book for your model.

if it functions correctly, add in a vacum guage on the actuator side of the vacum line, with a stone cold motor (20c) drive it easy and your vacum guage should read about 16 to25 hg for 80 seconds or so and fall to zero after the 2-3 shift. If it dosen't start looking at electrical funtion of the switchover valve (activated by HFM/SFI) and put 12v and ground to the valve to make sure it works. (benz also says to add in a DVOM to see the votage provided by HFM).

I've recently had my butt kicked by a repeated upshift fault and am pretty familar with the players. HFM, ECT, bowden cable, vacum dist. block, DM and the swichover valve.


Joe

First of all, the 95 C280 does have the upshift delay. Secondly, it's the 2nd-3rd gear shift that is delayed.

Eric,
Would you mind telling me your mechanic in Newport? Thanks.

David,

My mechanic in Newport is Strasse Automotive at 629 Ohms Way. They're actually on the Costa Mesa side of the border -- near Hoag Hospital. It's a small shop with 3 mechanics including the owner, Stan, who's a former racer.

I've used them on a Porsche, 2 Audis and 2 MBs for nearly 30 years. They're not magicians and don't always get everything right the first time (tough diagnoses sometimes take a few tries). But they're as stubborn as I am, stand behind the work, and usually come through. Unfortunately, Stan's just had a change in personnel on both other mechanics, including the one who works on MBs. So I'm watching the new guy carefully. I've had my diesel in there once under the new mechanic and it's too soon to know if he's up to Stan's standards. As Paul suggested, I've been known to print notes from this forum and bring them in. We'll see how the the new guy deals with that! This will happen first week in April. I'll keep you posted.

"First of all, the 95 C280 does have the upshift delay. Secondly, it's the 2nd-3rd gear shift that is delayed. "

David, reread my post, I clearly stated the 95 c280 has no 1-2 upshift delay.

And just for yucks, the .6 of 96 up production has it as well, only it's software driven.

Joe

Ohhh I see now. Everyone always thinks that's it's the 1-2 upshift delay, so I thought that you were referring to the delay, and that my car does not have one.

Miscommunication.

:o :)