Questions regarding 722.6 EGS51 TCU

[190EVAN]

Hello,

I’ve had trouble finding a suitable replacement TCU for my 1998 R129 SL500 with the 722.6 transmission. I purchased another TCU with the identical hardware number 0175450732 but a slightly different software number.

The original software number is 97W31… my dilemma is I am unable to find a replacement TCU with the same software number online. I tried a replacement TCU from another 1998 SL500 but with the software number 97W37 and it did not work.

From what I understand it is not possible to recode the EGS51 TCU’s to match a different vehicle.

Does anyone know if it is possible to recode them? This car is basically bricked until I figure out a solution to this TCU problem.

Should I maybe just return the TCU I purchased, buy another software version and try it out?

 

[gsxr]

If the TCU part number is identical, but has a different software coding... YES, I think you can "recode". There is a menu in HHT-Win that should allow copying the software code from the old module to the replacement module. I did this successfully on a 722.6 TCU for the W210.072 chassis, the procedure should be the same for your 129.067 chassis. You need SDS with HHT-Win, the original TCU, and the replacement with the same part number (or, equivalent in the supercession chain). Follow the instructions on the HHT-Win screen.

 

[190EVAN]

I have attempted this with HHT-Win but without luck. From what I understand you are able to adjust the variant coding on EGS52 but not EGS51.

I will try and attempt it again but after talking with a Mercedes tuner I was told it wasn’t possible on the EGS51.

I first ran into this issue when performing a differential swap on a W140 S420, I installed a differential from a W140 S500 and after completion of the install I went to test drive it and found it was in limp mode and would not shift gears.

I purchased an S500 TCU thinking it would solve the issue given the differential portion of the variant coding would match but it did not work. Out of desperation to get the car fixed, I tried a TCU from our 1998 R129 SL500 and somehow it worked in the diff swapped S420 perfectly.

Now I am trying to find a replacement TCU for the SL but am unable to find one with identical software numbers.

I’ll see if I can mess with it in HHT-Win when I receive the used control module I purchased off of eBay.

 

[gsxr]

The module I copied coding on was EGS51, so it definitely is possible, with at least some EGS51 TCU/EGS modules.

The coding includes data which tells the module what the rear axle ratio is. If you change the gearing, you need a matching program in the TCU/EGS, as you discovered with your differential swap. Sounds like you have something similar going on with the R129. Your 98 SL500 has 2.65 gears, same as the S500.

 

[Markus-MD]

normaly the egs 51 is plug and play. What you need is an TCU from a Petrol car with the same Diff Ratio. Diesel has other Can Protokoll

 

[Markus-MD]

and forgot you need this for a 5W580 also V8 cars not fro 6 or 4 Zylinder cars .-Here are the Ratios different 5W330 named

 

[190EVAN]

Thank you guys for the input. Initially I purchased a used TCU from an S500 as it matched the 2.65 differential I swapped into the S420, but it did not work.

Given your guys’ input I presume the used S500 control unit I purchased may have just been faulty/corrupted rather than incorrect.

I have reason to believe the only variant coding that really matters all that much is the differential ratio setting. I had thought that the engine output difference between the 4.2L and the 5.0L may have an affect on the TCU but it doesn’t appear to have any noticeable effect.

and forgot you need this for a 5W580 also V8 cars not fro 6 or 4 Zylinder cars .-Here are the Ratios different 5W330 named

Excuse my misunderstanding Markus but could please elaborate on this message? I appreciate the input but I am unfamiliar with these 5W580 and 5W330 numbers. Are these 722.6 variants or control module variants?

 

[Markus-MD]

4 and 6 Zylinder Engine have a smaller 5 G Gearbox it can Handel aproxx 330nm Also 5W330 only the V8 and V12 used the Bigger one 5W580 this can handel up to 580nm. The 580 is bullet Proof of all naturaly aspiratet Engine. The last one 722.643 was used for the e55 Kompressor .the .648 was used in Mc Laren SLR.and and both was proof 700 or 750 nm. The .649 was fitted in the early V12 Twin Turbos M275 -S/Sl Class. The .649 can handle 1000nm but is ca 2-3cm longer as all others.

for you is only the v8 5W580 possible. This TCU EGS 51 was made for ME1,0 Motronic and the can bus was similar the same. But you must look what shifter you have PRND1234 or PRND + and -.The later ones comunicates via Can with TCU.The early one with differnt Logic Pegel. In my History if you have an E Class you need an E-Class you cant take one from an S-Class .Funy Fact from R129 Sl fit and work .Easy check car wont start TCU fail. Wrong car. Shift only up too 3, gear wrong gear Ratio. V8 only 3 Typs 2,65/2,82/3,06

My expirience is that nobody can change with Star or other Diagnosis the Diff Ratio from EGS 51.Some Russian guys as Found a Solution but was an Hardware with reprogramming the intern Chip. The EGS 52 you can change the Software over VARIANT CODING. But no, never the EGS 51

Which Part Num. you are searching?

 

[190EVAN]

4 and 6 Zylinder Engine have a smaller 5 G Gearbox it can Handel aproxx 330nm Also 5W330 only the V8 and V12 used the Bigger one 5W580 this can handel up to 580nm. The 580 is bullet Proof of all naturaly aspiratet Engine. The last one 722.643 was used for the e55 Kompressor .the .648 was used in Mc Laren SLR.and and both was proof 700 or 750 nm. The .649 was fitted in the early V12 Twin Turbos M275 -S/Sl Class. The .649 can handle 1000nm but is ca 2-3cm longer as all others.

for you is only the v8 5W580 possible. This TCU EGS 51 was made for ME1,0 Motronic and the can bus was similar the same. But you must look what shifter you have PRND1234 or PRND + and -.The later ones comunicates via Can with TCU.The early one with differnt Logic Pegel. In my History if you have an E Class you need an E-Class you cant take one from an S-Class .Funy Fact from R129 Sl fit and work .Easy check car wont start TCU fail. Wrong car. Shift only up too 3, gear wrong gear Ratio. V8 only 3 Typs 2,65/2,82/3,06

My expirience is that nobody can change with Star or other Diagnosis the Diff Ratio from EGS 51.Some Russian guys as Found a Solution but was an Hardware with reprogramming the intern Chip. The EGS 52 you can change the Software over VARIANT CODING. But no, never the EGS 51

Which Part Num. you are searching?

Exactly the response I was looking for, thank you Markus!

Yeah I thought it was odd that the R129 TCU worked normally in the W140 too, but it was a long shot and I needed to get the car running so I just threw it in and tried. The diff ratios matched between the R129 and the W140 so I figured it was worth a shot.

The TCU I was searching for is 0175450732 with a 97W31 identifier. I found an R129 TCU with a close identifier that I just purchased off of eBay that I’m going to try. I have not been able to find an identical replacement TCU to the one I removed initially so I just have to attempt to make a similar one fit…unless I can figure out how to code it which I don’t believe is possible from what you said in your reply.

So, I’ll hope for the best with this new TCU and go from there.

 

[190EVAN]

If the TCU part number is identical, but has a different software coding... YES, I think you can "recode". There is a menu in HHT-Win that should allow copying the software code from the old module to the replacement module. I did this successfully on a 722.6 TCU for the W210.072 chassis, the procedure should be the same for your 129.067 chassis. You need SDS with HHT-Win, the original TCU, and the replacement with the same part number (or, equivalent in the supercession chain). Follow the instructions on the HHT-Win screen.

I think glossed over your quotation marks when you said “recode”, I realize now your talking about copying the software onto a different TCU.

I was a MB dealer tech for years so when I think of variant coding I think of actually modifying the coding in Xentry (this case HHT-Win) using the dropdown menus or manually inputting data.

So you’re basically referring to doing an initialization of a new module using the old one’s software. I hadn’t thought about attempting that albeit it seems like a great option to have if just plugging the thing in doesn’t work!

Thanks!

 

[Markus-MD]

 

[gsxr]

The TCU I was searching for is 0175450732 with a 97W31 identifier. I found an R129 TCU with a close identifier that I just purchased off of eBay that I’m going to try. I have not been able to find an identical replacement TCU to the one I removed initially so I just have to attempt to make a similar one fit…unless I can figure out how to code it which I don’t believe is possible from what you said in your reply.

The "identifier" you note above is just a production datecode. In that example, the TCU was manufactured the 31st week of 1997. The datecode is basically irrelevant, all you care about is the part number. For a given application, you need either the matching part number, OR a functional equivalent within the EPC supercession chain (newer/later ones typically have updated software versions). I believe in general you would always want the same or newer part number (first 3 digits identical or numerically higher). It's possible that trying to copy to an older module might not work - I'm not sure, never tried that.

I think glossed over your quotation marks when you said “recode”, I realize now your talking about copying the software onto a different TCU.

Yes! That is exactly what I meant. Thankfully, MB doesn't "lock" the software version/coding on the EGS51 TCU like they do with the ECU (ME 1.0/2.x).

I was a MB dealer tech for years so when I think of variant coding I think of actually modifying the coding in Xentry (this case HHT-Win) using the dropdown menus or manually inputting data.

Correct - variant coding is different. That applies to various later modules, not the EGS51.

So you’re basically referring to doing an initialization of a new module using the old one’s software. I hadn’t thought about attempting that albeit it seems like a great option to have if just plugging the thing in doesn’t work!

New modules from the dealer arrive uncoded, and the HHT-Win copies the existing coding from old module to the new one. However, this ALSO works with a used module that was coded differently (again, same module part number, but different software version coding). I successfully copied coding from one used module (in the car) to another used module (from eBay, with the same part number). The scenario I was dealing with was similar to yours, a different gear ratio. The copied TCU worked as expected.

 

[gsxr]

Sample screenshot from HHT on the EGS51 TCU for my 210.072 chassis. The first screen just identifies the module part number, and HW/SW versions. Note the module production datecode is not shown (i.e., 97W31). The Function Software identifiers are what will copy from old to replacement module (Data Set, ETC Coding, and Revision).

Unfortunately, it is not possible to manually enter the 3 values. They must be copied from an existing module. If you lose, or otherwise do not have, a TCU with the correct / desired coding... you're screwed. Manual entry (variant/SCN coding) and the ability to change the variant coding came years later.

I have a chart somewhere that shows some of the function software values for assorted mid/late 1990's EGS51 chassis/engine combinations. I need to find that and upload it to my website for reference.

 

[190EVAN]

The "identifier" you note above is just a production datecode. In that example, the TCU was manufactured the 31st week of 1997. The datecode is basically irrelevant, all you care about is the part number. For a given application, you need either the matching part number, OR a functional equivalent within the EPC supercession chain (newer/later ones typically have updated software versions). I believe in general you would always want the same or newer part number (first 3 digits identical or numerically higher). It's possible that trying to copy to an older module might not work - I'm not sure, never tried that.




Yes! That is exactly what I meant. Thankfully, MB doesn't "lock" the software version/coding on the EGS51 TCU like they do with the ECU (ME 1.0/2.x).




Correct - variant coding is different. That applies to various later modules, not the EGS51.




New modules from the dealer arrive uncoded, and the HHT-Win copies the existing coding from old module to the new one. However, this ALSO works with a used module that was coded differently (again, same module part number, but different software version coding). I successfully copied coding from one used module (in the car) to another used module (from eBay, with the same part number). The scenario I was dealing with was similar to yours, a different gear ratio. The copied TCU worked as expected.

Man thanks so much for clearing this up. I was really thinking the “identifier” was something more serious than a date code… makes perfect sense in hindsight.

 

[gsxr]

Found my variant coding docs, uploaded PDF here. Screenshots below.