What ever codes you could pull I do not beleive they will tell you the problem @ hand..

Do you have spark? Fuel? Compression...???

Jonathan

 

Welcome, to take advantage of all the forum features, please re visit the 'Welcome to the Forum' tutorial sticky on top of the W126 page, as well as the two DIY stickies.
It will show how to search the forum, and even has a link to the Russian MB site where you can run a VIN#. The forum archive has a wealth of information re your topic.
Good luck

 

Vsat-

Here is a fault code list that I got from somewhere about a year ago. On my 560, there's a black box with a cover about 4-5 inches long by about 1 inch that sits behind the primary firewall and about six inches inboard of the battery. If you take the cover off, there's a small pushbutton switch on top, and a red LED next to it. My memory is vague right now, so you'll have to check around, and I'm not sure if any of this applies to the 300 you have.

Jonathan is probably right, this fault code system might not give you any appropriate information, but it's something to play with, anyway.

Display Diagnostic Code
1. turn-engine off;
2. turn ignition switch to #2 position (do not start car);
3. depress switch (at diagnostic port) for 1-second, then release;
4. count number of LED blinks before going to solid/always on;
5. depress switch again to see if there are any other faults in memory (faults are displayed in descending order, and if there are no other faults in memory, the first fault number should re-appear);
6. record the number of blinks you counted for history;

Erasing/Resetting Check Engine Light
within 20-seconds of LED going to solid/always on,

1. depress switch for 6-10 seconds, release;
2. LED should blink ONCE then go to solid/always on;
3. turn ignition switch off;
4. restart car and verify that Check Engine Light is OFF (assuming you have CORRECTED the problem).

Here are the error codes.
Count the blinks after pressing the diagnostic button for 1 sec.

1. No Malfunctions;
2. Full load contact, throttle valve switch implausible;
3. Coolant temp. read by CIS-E implausible;
4. Potentiometer voltage implausible;
5. O2-sensor signal implausible;
6. Not Used;
7. TNA-signal (RPM-signal) read by CIS-E implausible;
8. Altitude pressure signal from EZL control unit implausible;
9. Current to EHA is implausible;
10. Idle contact, throttle valve switch implausible;
11. Air Injection System;
12. Absolute pressure values from EZL is implausible;
13. Intake air temp. reading is implausible;
14. Speed signal read by CIS-E is implausible;
15. Not Used;
16. EGR
17. O2-sensor line shorted positive to ground;
18. Current to idle speed air valve is implausible;
19. Not Used;
20. Not Used;
21. Not Used;
22. O2-sensor heating current implausible;
23. Short circuit to positive in purge switchover valve circuit;
24. Not Used;
25. Short circuit to positive in start valve circuit;
26. Short circuit to positive in shift point delay circuit;
27. Data exchange between CIS-E unit & EZL unit interrupted;
28. Intermittant contact in coolant temp. sensor circuit;
29. Difference in coolant temp. read between CIS-E unit & EZL unit;
30. Not Used;
31. Intermittant contact in intake air temp. sensor;
32. Not Used;
33. Not Used;
34. Coolant temp. from EZL unit is implausible.

 

Hi Dave, could you post this in the DIY?

BTW, did the idle valve make a difference?

 

Teutone--

I will certainly do that, but now that I've posted it, I'm not sure if this is the code list I got for my parents' 1995 E320. If someone (Jonathan?) could confirm that this is correct for a 126, then I'll do it.

Dave

(edit) No, the valve didn't seem to make a difference (check your PM).

 

Thanks Guys!!! Yes I have fuel compression & spark. The plugs are black but not wet. Engine will start after an extended crank & idle smoothly, but when I try to rev the motor it just gags & quits. No backfire though. One time I nursed it along by giving it slightly more gas each time & bringing the revs up slightly each time until it did rev up and run well. I drove it about a block & it quit & wouldn't restart. I know it's running rich and suspect too much fuel pressure, a leaky cold start valve or possibly a bad O2 sensor. That why I wanted to check the codes. I just bought it for a great price. It's a very clean car with zero rust, a super nice interior & only 138k on the clock. I used to be an MB line tech back in the day & am familiar with CIS. I've ordered the service manuals on DVD but they haven't arrived yet. In the meantime, I'm enjoying this websight. Big fun! Thanks again,Vince

 

I'm not certain, but I do not believe the 88 has the push button..I think that only came about later (90/91) and prior to that only on cali models.

I think all he has is the round pin plug on the drivers fender well leaving you w/ very limited info to pull :-/

You can pull the cold start and plug the hole easy enough.. A bad O2 won't make the car run That poorly. If you suspect it's fuel your BEST bet would be to get a set of fuel pressure gauges on there and go through the respective tests to see what aspect of the system is not functioning properly.

Service manuals on DVD eh? The W126 manuals come on CD so I'll be curious to hear what arrives!

Best of luck!

Jonathan

 

The codes list is likely for the 1995 E320 m104 cis engine, and unlikely to yield as much info fom a m103 diagnostics port which barely has 7 pins.

fuel is an easy test (take precautions here) - remove the 17mm fuel pipe connection on the side of the fuel distributor and turn key to pos II and crank...if fuel pump/fuel pump relay are fine, fuel will pump from this pipe. My Widebody SEC wouldn't start last weekend...undid the fuel pipe conenction on the fuel distributor and no fuel....checked voltage at pump on cranking, absolutley fine....but pump was seized solid. Changed pump and all fine. Not much more else in the system to diagnose.

For ignition, test for spark at one of the spark plug leads and at the main coil lead on the dizzy cap. Failure of spark at plugs could be failed dizzy cap/rotor arm. Failure of spark at dizzy cap could be coil / crank position sensor or ignition EZL.


talbir

 

Also, if it starts and runs spluttery, OVP relay can be faulty...fuse in it might be fine, but the OVP relay controls the fuel injection system, so when that relay is faulty, the engine just won't run right and one of the classic symptoms is stalling on any attempt to rev the car.

The OVP relay is located by the wiper motor.

 

Instructions to check the OPV are in the DIY sticky. Have you checked the ingition coil? Mine was having difficulty starting. When I sprayed the terminals of the coil with contact cleaner, it started right up. Checked the ignition coil and it was out of spec.

 

Hey, thanks again everyone. I really appreciate the info. 1st, the DVD's arrived but the problem is my PC runs on Vista. Can't load it. Theres nothing in the e=bay description about that. I should have done more research before I bought. I'm going to give them away to someone on this site as soon as I get a chance (probably tomorrow). I am going to register the car on Mitchel's DIY if I have to. I've used it in the past and it's pretty good. Meanwhile I'm going to do a pressure/volume test on the fuel pump. If that's ok I,m going to get an OVP relay and try it. I looked at it and both fuses are good, but as you guys say, it still might be NG. Finally, the port for the codes was exactly where I was told, I followed the directions and got 1 blink (no fault codes) which is what I expected as the CEL wasn't on. Once again, thanks for everything. I'm really enjoying this sight. I find myself checking it out for hours on end. Like I said before BIG FUN., Vince

 

About the CD:
I always do an "explore" on the disc then "open" then choose "opening".
Mines never work on XP, nor on Vista and they are the original CD discs.

About the car:
What is the spark plug gap? And what brand are the spark plugs?

 

vsat-

Glad to hear that you found the code box-- but one blink does mean no faults.... Apparently, the list I gave is not for the 126 (thanks, Talbir). As far as the MB disks, too bad your PC won't run them. I'm now a Mac convert, and problems like what you've had are the main reason. Why can't Vista load the disks? I recall simply transferring files and then getting a special directory device from Steve Nervig's website.

Mercedes-Benz Service Library Index Download Page

If you do a search for "CD manuals" you might get some great info. If you have faulty discs, there are members on this site that have been able to get their hands on a *cough* spare set and send them along gratis.

 

You may need to install Adobe's Acrobat Reader.

 

vsat-

Here's another attempt at the codes thing- I found an old link that I remember from my searches last year. It should be helpful to you...

http://home.comcast.net/~chwilka/Error_Code _reader_reset_tool.htm#Fig-1

Good luck with getting your ride healthy!

Dave

I'm also going to make a sticky for this, Teutone...

 

I want to thank everyone for all the help. Turns out the aux air valve was stuck open, giving it a major vacuum leak. Took it off and cleaned it, re-installed it, vroom. Car runs like a champ. I've been driving it the last few days. It runs perfectly. I'm in love!

 

Fault codes for s 1988 560SEC

This message is in response to ElRojo comments he posted in 2008 about the fault codes for his W126 560SEL: I have a 1988 560SEC, my question is: are the fault codes you listed on your post the same for a 560SEC?

Does anyone know where to obtain the full confirmed list of fault codes for my 88 560SEC?

Thanks in advance for any help!

Cherry2728

 

I'm almost positive that the second post I made had the right set... Here it is again. In the 560 SEC, the set will be the same, and I'm pretty sure the max. number of blinks is 12.
Comcast.net: Personal Web Pages)

Best of luck!

 

FAult Codes out of X92 connector

Dear ElRojo: thank you so much for the re-posting of the thread about fault codes for my 560SEC 1988. I used the push button on the X92 connector next to the battery and returned a count of "4", meaning my CIS air flow meter flap potentiometer is not "plausible" (wonder what they really meant in German with that word!).

Also, do all the remaining codes (SRS and ACC) will flash from the same X92 connector once I press the little push-button? Or do I need to use the LED and Switch as you described in the thread. This is a California version not Federal and I thought that for the Californians, all the codes will come out on the built-in LED without the need for external LED/Switch assembly. Please clarify if you know.

Thanks,

Cherry2728

 

Hi all...

This site seems to have some folks who might know what my car's problem is. . . So I'm gonna give this a shot.

I have a 1988 Mercedes 300se with 160,xxx miles on it. For a couple months now my benz will just turn off while driving. Doesn't matter how fast or slow I'm going, or for how long the car has been running on a particular trip. . . It will at times just die while driving on the road. It always starts back up after waiting a minute or two, and will sometimes die just once during a drive or over and over..& some days it doesn't die at all.

The car makes no warning sounds or feelings before dying..it just dies.

I don't know much about cars especially this one as I have only owned it for about 5 months. So bare with me.
I went under the hood and checked the blinking light code thing near the firewall on passenger side. I turned my key two clicks and pressed the button for a couple seconds and the led light flashes 5 times and then stays on by a number 4.

After reading a post above with some code readings I am assuming it's saying I have a problem with an O2 sensor signal implausible
Not sure what that means? I need to replace an O2 sensor?

Don't have the money to take the car to a shop at this time..so seeing if I can find the problem myself ..then I can have my bf fix it. He's not familiar with this type of car either. But has fixed other things on it for me and it has worked out...so hoping we can tackle this ourselves.

I've asked some parts stores about the stalling issue and they have all been baffled and not much help.. anybody have experience with this?

Does the led error code sound like a good place to start?

Any knowledge shared will be greatly appreciated.

Thank you in advance

 

You should start your own thread for this problem as it doesn't follow from the subject of this thread.

Fill in your user profile so we don't have to remember what car you have.

As far as I know, the O2 sensor cannot make the car shut off. I'd look at the fuel pump relay and the crank position sensor, for starters.

 

For my 89 300 SE to pull fault codes I had to make a wire harneas with a momentary pushbutton and an LED in parallel with banana plugs on either side. Between the firewall and the cabin, near the battery there is a rectangular plastic block with I believe 7 ports. If you plug in the negative side of the harness to port 1 and the positive side to port 3 the LED should blink a number of times indicating a code. But as others have said this code likely be much help with a no-start. If this doesn't make sense let me know and I can post some pictures.

 

From Starfinn's description I believe this is under the hood, a handy factory gadget to have. I'll 2nd John's idea on the fuel pump relay, the 300SE I had had one go bad and it was a similar problem of running sometimes, sometimes not. I'm not sure if the 88's had the MAS or a "regular" relay

 

Only CA cars have that test panel Bruce. You can make one however though.. In case it does not exist on your car. They are easy to make and about ten bucks in parts from Radio Shack, if you can find one left anymore.

The FPR is easy to test. Just jumper the two pics 7-8 I believe. If the pump comes on, the FRP bad.

 

Hello El Rojo!
I read this thread you posted a while ago. Very informative! The first challenge is finding out how to take the cover off the exposed the button you mention?
Any help would be greatly appreciated
Sven

 

Buddy, the post you're replying to was twelve years ago.

Anyway, my 300SEL has that button and light, but it seems to be dead. Light doesn't light up and there's no current at the terminals. Maybe a wire is cut. Hasn't been an issue for me since my engine runs perfectly.