After doing a little more reading, I have seen that there are also 38 Pin ports on the W140 that are OBD2 systems. How can I determine if my 1996 S500 W140 has an OBD1 or OBD2 system?

I have found this OBD2 38 Pin Diagnostic Reader on a YouTube video

that looks like a good solution. However, I can only buy this if my car has the OBD2 system.

 

The 38 pin is not OBD. It is propriety bus to Mercedes only.

The OBDII system for these cars was put under the steering wheel, but on the dual port cars(OBD2 and 38 pin) all deep codes like transmission are handled by the 38 pin, and you need a MB Star unit to clear codes. All limp mode transmission codes must cleared with MB Star unit no mater if installed new parts, or Mercedes parts.

The cost effective unit is the one on post 14(get it from that link). I have that one purchased from that link. The vendor is safe. Others exist on the market, but are not reliable, and prone to failure. I have used mine on many cars...

https://www.benzworld.org/forums/r129-sl-class/2315329-got-my-mb-star-c4-diagnostic.html

Buy it configured for a Dell D630, and buy your self a working D630 of ebay. Duplicate the hard drive as they load the software on used hard drives.

If you need support, post on that link above. Many people there on that thread are smart. Paul600600 is the genius, and he sells a turn-key unit ready to go if that is too much for you.

Best of luck,

Martin

 

Thanks for this very helpful information, Martin. Much appreciated.

I am going to need to go with a much lower cost solution for diagnostic testing as I will only be in Saudi until next May ... I will be forced to sell the S500 just before leaving. Essentially, I need to get through the next few months with a low-cost solution to diagnose any issues before taking the car to mechanics who are notorious for trying this and that to fix MB cars as the shops do not invest in proper diagnostic tools like the MB Star C4 you have noted.

While perhaps not the best solution, I am thinking of at least getting this unit to offer me some feedback on what is happening with the S500. Mercedes 1988-1995 OBD1 code reader

Off topic here but this is the reason I started looking for an OBD diagnostic tool. Transmission Gear Clunky Shifts and Limp Mode Incident.

I should note that after turning off the car and waiting a few hours before restarting, the Yellow ASR light has not since lit up and the Limp Mode has not returned ... so far. I have driven the car three times since the one time only Limp Mode incident. Previous to the Limp Mode, the Yellow ASR light had been coming on after a few minutes of driving the car with this happening over the last few weeks on a regular basis. Sometimes the Yellow ARS light did not come on.

If the issue of the Yellow ASR light coming on and the one-time Limp Mode activation occurrence are transmission fault issues, then I plan to start by changing the 13 Pin Connector on the transmission alone with the tranny filter and gasket and see if this resolves the issues.

A few symptoms regarding the transmission behavior are likely worth noting.

1) The shifting from 1st gear to 2nd gear and 2nd gear to 3rd gear feel clunky ... not smooth. 1st to 2nd is smoother than 2nd to 3rd gear.

2) The transmission rarely seems to go into 4th gear although this may be because I do not drive the care over 110 kms per hour and the rpms are around 2,100 at that speed. Maybe a little higher at 2,300 but certainly not higher than this. I have on a few rare occasions driven the car faster and barely noticed a gentle smooth shift into 4th gear. I am wondering is this should be the way the 1st gear to 2nd gear and 2nd gear to 3rd gear shifts should actually perform and feel like .. smooth and barely noticeable. I am considering adding a quart of Trans-X Automatic Transmission Slip-Stop and Leak Fix as recommended by Kent Bergsma on his YouTube channel video

This idea does scare me a bit as I worry I may end up making the transmission worse instead of better.

As noted, my original intention was to find a low-cost diagnostic solution to try to establish what is going on with the transmission, Yellow ASR light coming on, and the Limp Mode incident. That being said, the immediate concern is to find out what is going on with the 722.6 5-Speed transmission.

Car has 224,000 kms on the odometer. Just over 139,000 miles.

 

You might be able to get by with a blink counter code reader sold on eBay. I think there are instructions on how to make one on YouTube. Basically, you hook it up to specific pins for the function you want to test, and count how many time it blinks to get the codes. There is a generic table of codes somewhere in the DIY sticky under maintenance manuals, I believe. It's a pretty tedious way to get codes, but it's cheap. You can also clear codes with it.

There used to be some other code readers that could read Mercedes codes, but I'm not aware of anything currently available that can, certainly nothing like the Star system.

Here's a YouTube link for a diy reader.

 

You might be able to get by with a blink counter code reader sold on eBay. I think there are instructions on how to make one on YouTube. Basically, you hook it up to specific pins for the function you want to test, and count how many time it blinks to get the codes. There is a generic table of codes somewhere in the DIY sticky under maintenance manuals, I believe. It's a pretty tedious way to get codes, but it's cheap. You can also clear codes with it.

There used to be some other code readers that could read Mercedes codes, but I'm not aware of anything currently available that can, certainly nothing like the Star system.

Here's a YouTube link for a diy reader.

https://youtu.be/HDTS02fdLDw

Thanks so much, jal1224. Much appreciated.

 

Here's another link with code info.
https://www.k6jrf.com/MB_X11.html

 

Check with MAVA about how many systems you'll be able to check with the blink tester. Mercedes gradually changed over the years from analog to digital modules, and blink testing became more limited, as I recall. If you also have the OBD 2 connector under the dash, I'd check it also with a generic tester, to see what engine trouble codes it reveals. I know US cars came with the OBD2 connector in 1996, but I'm not sure about RoW cars.

 

Thanks, jal1224

I have searched all areas under the interior dashboard on both the driver's side and passenger side and there is no 16 Pin OBD2 connector. The only OBD is located under the hood in the engine compartment in the F23 Module housing. There is a cap that can be removed from the F23 module housing to access the 38 Pin connector port.

https://www.justanswer.com/mercedes...com/mercedes/1dynq-mercedes-s500-vin-its-not-control-module-cruise-control.html Picture shows F23 Module Housing with round cap for removal to access the 38 Pin connector port.

Yes. I expect that the basic "Blink Test" solution will be rather limited for diagnostics. But at least I can assess a few areas of the car to see if there are additional issues that need addressing beyond the obvious transmission hard shift issue, the one-time Limp Mode issue, and the previous Yellow ASR dashboard light illumination issue.

Japanese Import Car

This MB S500 W140 is a Japanese import car. All the decals on the sun visors and door plate info are in Japanese language.

I suspect that while my W140 is a 1996 model year that it was a late run 1995 build for the beginning of the 1996 model year and therefore does not have the 16 Pin OBD2 port. The other possible issue, this may be a 1995 model car and the Saudi Arabian registration system just has it wrongly listed as a 1996 -- entirely possible here. I will need a solution to run the VIN number and see if I can be sure which model year this car is.

 

Hello, Martin.

Just a wealth of very helpful and insightful information. Thanks so much.

I am getting to work on going through each item one-by-one and remain hopeful that I will successfully resolve all issue. Will keep the thread updated as I get more details and results.

All the best,
David

 

David,

You are welcome. Hope it helps you fix your problem in a cost-effective form..

Martin

 

Yikes!

Did the Reset on transmission shift points a few time and the car definitely improved for power but shifts were still hard. Tried doing the reset a few times and sometimes the engine felt sluggish afterward and other times the engine performed nice and strong. Never any improvements on the hard shifts.

Yesterday, I removed the TCU unit to inspect for transmission oil and the unit and the wiring harness are dry and clean. No issue there. I also removed the ASR module and the module closest to the firewall, maybe the Base Module .. not sure, and all units were clean and dry.

After reinstalling all three computer modules, the ASR light on the dashboard was on all the time unlike the previous situations where the ASR light would only activate after driving the car for a few minutes. Now it is on as soon as the car is started and it stays on all the time.

I decided to do another transmission reset today and "Oh No" ... now the transmission will only shift from 1st gear to 2nd gear ... no 2nd gear to 3rd gear. I tried resetting two more times and no change. I only have 1st to 2nd gear. I drive the car up to 100 kms per hour to see if 2nd gear would shift to 3rd gear at a higher rpm but no luck.

As I am not starting in 2nd gear I do not think I am in Limp Mode but perhaps I am wrong.

The question now becomes, where do I go from here? I will follow the steps MAVA has offered in his feedback. I think I should start a fresh thread post as this thread has moved way off the original topic.

Will post new thread as 722.6 Transmission Not Shifting Past 2nd Gear

 

If you are stuck in a mild 2nd on occasion, you must have a conductor plate failure, and/or broken spring.

You need to pull the valve body down for inspection,

Martin

 

OK. Well, that certainly points me in the right direction for the heart of the issue, Martin. Thanks so much.

Do you think any of the solenoids on the connector plate may be an issue causing the shifting to not go beyond 2nd gear?

I just started a fresh thread on this transmission issue as this particular thread has moved off topic as I started this as an OBD1 to OBD2 topic. It may prove helpful to others searching threads if the discussion takes place in my new thread.

https://www.benzworld.org/forums/w140-s-class/3002795-722-6-transmission-not-shifting-past.html#post17547041

In this new thread posting, I have listed all the parts I was planning to change while the tranny pan is open. Perhaps you can offer your feedback, Martin.

 

Had the same question. It turns out that through the OBD2 port on the 140 you can only access the engien control unit. But if you want to access all systems you can use the youcanic scanner and their multiplexer as shown in this video: