Mercedes-Benz 722.6 Transmission FAQ - Page 34 - Mercedes-Benz Forum
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post #331 of 352 (permalink) Old 02-23-2017, 02:04 PM
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Gear wise you should be fine. The basket count of clutches where it matters is on B2 and B1 and the 607 has one more. Is it of concern? No... I would not worry... What matters is they are both from V6's...

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post #332 of 352 (permalink) Old 04-28-2017, 09:45 AM
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If they do not go away after you clear them (you did, didn't you ?) you then have persistent problems with the can_bus connection at the TCM. Hopefully it is a dirty connector (the one that has a pair of separated pins from the other which are for the can_bus. Have you touched the TCM (EGS52) to see if it was contaminated with ATF ? I guess you did. You call it "ECU". Just make sure the connectors to the TCM are clean and the plugs are installed properly. I would douse the connectors with electronic contact cleaner spray and let it dry prior to installation.
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post #333 of 352 (permalink) Old 04-28-2017, 10:14 AM
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ha!
yes i totally called it the ecu and thats what i checked for atf or other contaminants and it looked really clean and dry. i will clean it anyways, thanks for the tip!
and yes i cleared the codes a couple of times before starting the car, and they are right back after startup still in P.
if i clear them with the engine on ,it takes a while of driving for them to reappear.
oh and i just installed a new break/stop light switch but that did not change anything....
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post #334 of 352 (permalink) Old 04-29-2017, 02:23 PM
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quick question,
if i would get a used good TCM and swap it out to eliminate that as a cause for the issues, would it have to be reprogrammed by star or should it work plug and play?
i just have a icar soft mb2 diagnostic tool....
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post #335 of 352 (permalink) Old 07-05-2017, 12:45 AM
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Pilot bushing 7 mm bolt torque is now only 2.5 Nm. It was revised down in 2008.
Also,I find the drain plug 20 Nm torque setting to be unnecessarily high,resulting in difficult removal and rounding of the 5mm hex.
I have found 15 Nm is better.

Last edited by Benzyle; 08-01-2017 at 03:47 PM.
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post #336 of 352 (permalink) Old 10-26-2017, 09:34 PM
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1996 SL500 Limp mode

Quote:
Originally Posted by loubapache View Post
What Is Limp Home?

Well, that means, your car has lost a wheel so it is driving on three wheels to home.

Seriously, when the Electronic Transmission Control module (ETC) detects intermittent or active problems, it prohibits gear shifting, in order to avoid serious transmission damage.

There are two different types of Limp Home modes, depending how serious the problems are. The names of these two different Limp Home modes may sound counter-intuitive but that is what Mercedes used.

Mechanical-hydraulic emergency running mode
(This is the light duty Limp Home)

In this Limp Home mode, the transmission locks onto the 3rd gear or the last known “good” gear.

This particular Limp Home mode can be reset by turning the ignition off and then on.

This mode could set generic OBD II code and also intermittent code in the ETC.

Electric emergency running mode (This is the bad boy )

In this Limp Home mode, the gear engaged at that time is retained and the assigned fault code is stored. After a shutdown, wait for more than 10 seconds, and restart, the transmission is locked in the 2nd gear and reverse gear only. When the shifter is moved from “P” to “R” or “N” to “D”, there is a huge clunk.

The transmission will be in this mode until the codes are cleared from the ETC by Mercedes HHT (Hand Held Tester) or SDS (Star Diagnostic System) or some third party special scanners or even the reversely engineered ones. Generic OBD II scanners cannot clear these codes from the ETC (although they can clear the corresponding generic OBD II codes).

When the transmission is in this “electric” Limp Home mode, it feels like it is completely shot. Many times (actually I will go out the limb and say most of the time) you do not need a rebuilt transmission or a new ETC.

What to do if the transmission is in limp home mode?

The most useful thing to do is to have the ETC trouble codes read. This requires a Mercedes HHT (Hand Held Tester) or SDS (Star Diagnostic System) or some third party special scanners or even the reversely engineered ones. These codes are pretty accurate at pointing to the fault that caused the limp mode. For example, it may have codes for speed sensors or the shift module.

If no Mercedes scanners are available, at least try to read the codes using a generic OBD II scanner. The generic OBD II codes are not as precise as the proprietary Mercedes codes but they might shed enough light to have a good enough diagnosis. For example, if a code P0715 is read, then it is fairly certain that it is caused by the speed sensors.

After fixing the underlying cause of the (electric) Limp Home, the transmission would still not shift. The ETC has to be reset (codes cleared) before it will act normal again.

Without an ETC reset, people often (unnecessarily) replace the ETC. Of course, a new or working ETC will make the car shift again but all is needed to be done is to clear the codes in the ("bad") ETC. When the ETC goes into (electric) Limp Home, it shuts off all the power to the solenoids so the ETC will test "bad" because of this.

There are different versions of the ETC and certain ETCs can only work with certain valve bodies so exercise caution when replace either the ETC or valve body. It is a good idea to use the existing part numbers to find replacements.
I believe my car is in Limp mode, but my generic OBDII scanner does not generate any code whatsoever. Is this something that I should clean the shift module and put it back? My original thread is at "1996 SL500 transmission"
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post #337 of 352 (permalink) Old 10-26-2017, 09:40 PM
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WD-40 into shift module

Quote:
Originally Posted by loubapache View Post
What Are The Common Problems of The 722.6 Transmission?

Although the 722.6 transmission on the W210 can have mechanical problems (especially those on the pre-2000 models), the majority of the problems are actually small or electric, especially if the transmission has fewer than 150k mi.

If a transmission has major mechanical problem, then the only options are to rebuild the transmission or to install a used/new transmission. The typical mechanical problems are noise and/or metal in the oil pan or filter.

The pre-2000 model years tend to have more mechanical problems than the post-2000 models. This is primarily due to some upgrades in shaft bearing and valve body in the post-200 models.

To rebuild the transmission or install an already rebuilt transmission, the existing transmission has to be removed first. "nhmercracer" posted a procedure to remove the 722.6 transmission.

Rebuilding transmission is above the average DIYer and should be handled by special transmission shops or dealers so this FAQ stops the major mechanical problem discussion here.

The shifter bushing is a minor mechanical problem that is easy to fix. Again G-AMG posted this Photo DIY: Shifter Bushing Replacement.

The three most common problems that a DIY can repair are

1) Pressure Regulator Valve Spring (This applies only to 1997, 1998, and 1999 models)



This spring affects the shifting from 2 <--> 3 and 3 <--> 4. If your transmission has rough shifting in these gears, then chances are this spring is either collapsed or completely broken. Here is a spring replacement DIY by JRS.

2) Electrics Kit, aka, Conductor Plate or Electric Plate (This affects all models)


722.6 Conductor Plate

The conductor plate is on top of the valve body and houses six solenoids and two sensors, a few other things. Common failures are the two speed sensors, which cannot be replaced separately so the entire conductor plate has to be replaced. This part has also received multiple updates so make sure you get the latest part.

When the speed sensors fail, the ETC does not know the input/output shaft speeds so it does not know what gear the transmission is in. If the failure is intermittent, then the ETC will go into Mechanical-hydraulic limp home mode. If the problem is more severe, then the ETC triggers the electric Limp Home mode.

Typical symptoms of speed sensor failure are erratic shifting or no shifting at all. The best diagnosis is to read the codes in the ETC using special scanners. If there are 012 (108) or 013 (109) codes, then the problems are likely the speed sensors.

If no special scanners are available, then at east read the codes using a generic OBD II scanner. Chances are the Check Engine Light (CEL) is on. If the codes are P0715 or P0720, again, the problems are likely due to the speed sensors. I said likely because the generic P0715 is mapped to several Mercedes codes. However, based on what has been seen, P0715 is a pretty reliable indicator of speed sensor failure.

Yours truly replaced the conductor plate on a 1997 E320 and you can find the instructions here.

3) Shift Module
(This affects all models, especially when you . . . )


Shift Module

This is sometimes called the liquefied module problem. Mercedes puts the cup holder near the shifter (for a reason) so you can spill your favorite drink into the shift module. Since the 722.6 is an electronic transmission and the shift module sits right below the shifter, unprotected and ready to receive your favorite drink, the favorite drink will cause the electronic parts in the module go crazy. The transmission could go into Limp Home mode and the CEL could turn on. If you check the codes, there could be some generic OBD II codes such as P0705, etc.

When this happens, you can try to take out the shift module and clean it thoroughly with electric contact cleaner and clear the codes in the ETC. If that does not work, you need a new shift module or a (working) used module.

Member covinsky detailed the procedure to remove the shift module.


P.S. "G-AMG" posted a combined Photo DIY- 722.6 Conductor Plate and Regulator Valve Spring R/R DIY.
Last time when I removed the shift modue to check if any drink spilled on it, I found some rust at metal compoments. So I sprayed good old WD-40 into the module and installed it back. Would it be the reason of Limp mode? What do I have to do in order to elimiate the WD-40? Blow the compressed air into it? How do I verify its function after that?
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post #338 of 352 (permalink) Old 10-27-2017, 06:20 AM
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As your car has non- touchmatic shifter, it should not have the electronic module in the picture of the post you referenced. If there is a problem with the shifter plausibility (what shifter TRRS module tells ,electrically, the transmission module what the gear selection is , and what the mechanically selected current gear is), there will be a code "114" from the transmission module, but it will not be mapped to a code to be read through the OBD2, meaning no OBD2 fault codes in this case.

1) Make sure that the shifter linkage is properly adjusted
2) Clean the shifter module connector with a contact cleaner and let it dry to get rid off all WD40 remains.

The TCU code can only be read with a proper scanner through the 38 pin connector.
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post #339 of 352 (permalink) Old 10-27-2017, 07:48 AM
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shifter linkage adjustment method

Quote:
Originally Posted by mrboca View Post
As your car has non- touchmatic shifter, it should not have the electronic module in the picture of the post you referenced. If there is a problem with the shifter plausibility (what shifter TRRS module tells ,electrically, the transmission module what the gear selection is , and what the mechanically selected current gear is), there will be a code "114" from the transmission module, but it will not be mapped to a code to be read through the OBD2, meaning no OBD2 fault codes in this case.

1) Make sure that the shifter linkage is properly adjusted
2) Clean the shifter module connector with a contact cleaner and let it dry to get rid off all WD40 remains.

The TCU code can only be read with a proper scanner through the 38 pin connector.
Hey, thanks.. Any particular easy method to adjust the linkage accurately?
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post #340 of 352 (permalink) Old 10-27-2017, 08:02 AM
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Check the following out

for 1) and 2)

Also check fuse 11 and voltage on fuse 11, which powers your shifter TRRS module.
Attached Files
File Type: pdf shift linkage adjustment.pdf (809.6 KB, 50 views)
File Type: pdf TRRS coding.pdf (730.3 KB, 54 views)

Last edited by mrboca; 10-27-2017 at 08:36 AM.
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