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Registered 1999 SLK230
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68 Posts
Discussion Starter #1
This winter, my SLK230 went into "limp mode" after starting. As soon as I put it in gear, there would be bump and the transmission would stay in 2nd gear. This turned out to be a ATF fluid overflow. After drawing fluid out with a pump, it ran fine for several months.

Now it's doing it again, but only after warming up. It wants to stay in third gear or above (hard to tell which one). The car will drive fine and then after about 15 minutes will give a lurch. Starting from a stop is sluggish, but driving at 30-40 mph is fine. Last time I tested the fluid levels and came out a bit low, so I added a trickle of fluid.

A test this morning has the same symptoms. Perhaps the fluid level is too low?

However, I'm getting inconsistent results reading my transmission fluid. Whether the transmission is hot or cold, I either read very little fluid, or the whole plastic part is smeared with fluid. I can't tell whether it needs more fluid or not.

The Check Engine light came on for the first time ever, too. When I find my code reader I can give more information.
 

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Registered 2001 SLK320
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889 Posts
This winter, my SLK230 went into "limp mode" after starting. As soon as I put it in gear, there would be bump and the transmission would stay in 2nd gear. This turned out to be a ATF fluid overflow. After drawing fluid out with a pump, it ran fine for several months.

Now it's doing it again, but only after warming up. It wants to stay in third gear or above (hard to tell which one). The car will drive fine and then after about 15 minutes will give a lurch. Starting from a stop is sluggish, but driving at 30-40 mph is fine. Last time I tested the fluid levels and came out a bit low, so I added a trickle of fluid.

A test this morning has the same symptoms. Perhaps the fluid level is too low?

However, I'm getting inconsistent results reading my transmission fluid. Whether the transmission is hot or cold, I either read very little fluid, or the whole plastic part is smeared with fluid. I can't tell whether it needs more fluid or not.

The Check Engine light came on for the first time ever, too. When I find my code reader I can give more information.

Just to clarify. Does it stay in third even when you have to stop? Can you downshift it manually to 2nd?
 

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Registered 1999 SLK230
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68 Posts
Discussion Starter #3
Yes, it stays in third when I have to stop. So after stopping at an intersection, the car starts very slowly. I've not tried to downshift manually, no.
 

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Super Moderator UK SLK 55 AMG 2007
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27,223 Posts
Has the tranny fluid ever been changed?


MB said 'for life' in the early days.

They said the same about the compressor too.
But those that serviced have found varying quantity and levels of fluid.

There are a couple of tsbs on the tranny.
One related to oil leaking into the electrical cable 'may' relate.

Another two, that may relate are about getting stuck in park (your symptoms may be early signs, not sure) and getting stuck in park (again, yours may be early signs).


I'll hit the experts button for the 170s.
@Mn car guy
@efair
@stu32
@savcom
@Turdo2
@Padgett
@Australian
@Dave2302
 

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Registered
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846 Posts
You will see a big difference in transmission fluid levels between hot transmission and cold. On the dip stick you would normally have indicators for each but hot should always be at the top mark. When you have read the fault codes it will help point in the right direction and remove much guess work.
 

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Registered 1999 SLK230
Joined
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68 Posts
Discussion Starter #6
Update: I drove the car for about 20 minutes until it went into limp mode. I didn't notice until I slowed to a stop and then tried to start moving again. The transmission was stuck in a high gear. The transmission shifted flawlessly until this point. When I returned home I did some experiments:
•moving the shift level into 1st, 2nd, or 3rd had no effect whether stopped or driving.
•Putting the shift into park or reverse activated "normal" limp mode, where it went into second gear.

I got out a hand pump and drained transmission fluid until the fluid level was between the two 80°C marks (though a bit on the high side). I removed the negative battery lead for a few seconds to clear any faults, then tried it again. It had been vastly overfilled. About half a spaghetti sauce jar was filled, so about 12 ounces of fluid.

The car is still in limp mode, unfortunately. I drained more fluid until it read on the lower end of the 80°C mark with no change.

The transmission was probably overfilled for months, but my work is less than a ten minute drive, so the transmission never got a chance to warm up. I will have to read the code to get more information.
 

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Registered 2002 R170 SLK V8 5.0
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2,593 Posts
Hi,

Removing Battery does not clear codes, in fact it usually does more harm than good, particularly on Cars with more electronics.

I wouldn't call half a jar vastly overfilled, as has been said before get it read on equipment that can actually read it, IMHO SDS.

Everything else is pure guesswork and speculation :wink:

HTH, Cheers Dave
 

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Registered 1999 SLK230
Joined
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68 Posts
Discussion Starter #8
Thanks for the replies, all
I borrowed a code reader and got a single code: PO715 which indicates "input turbine sensor A"
Reading other posts, it has to be the "infamous conductor plate" issue.

I watched a how-to video. It looks like this is a job I could do myself. I don't have access to a car lift, so things'd be tight.

I can order a replacement here
https://www.rockauto.com/en/moreinfo.php?pk=9642788&cc=1356476&jsn=402

Any advice as in "yeah, you won't even sweat! or "don't even think about doing this yourself because..."
Paying $1600 to a MB mechanic is doable, but the nearest one is 30 miles away.
 

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Registered 2002 R170 SLK V8 5.0
Joined
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2,593 Posts
Hi,

$1600 sounds hellish expensive ................

It is 2 hours max, plus

Oil, Filter, Connector Plug, Pan Gasket, Conductor Plate.

Codes will need clearing, should be included in price ;)

HTH, cheers Dave
 

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Registered 1999 SLK230
Joined
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68 Posts
Discussion Starter #10
From other posts I've read on this forum, $1600 is about right unless someone has a different experience.

I found a more detailed video

I'm seriously considering attempting this myself. If I can get high enough ramps, it's just wrench-work.
Has anyone done this at home?
 

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Super Moderator UK SLK 55 AMG 2007
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27,223 Posts
Circa £1280.

Guesstimate 2hrs labour plus typical dealer charge to clear codes (they do that) roughly £400.
So, parts circa £900.
I know nowt, but that sounds dear.
 

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Registered 1999 SLK230
Joined
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68 Posts
Discussion Starter #12
Reading some posts, I was informed that a new part can't just be swapped in due to the anti-theft codes. I'd have to tow the car 30 miles away to the nearest independent MB mechanic to get the car reprogrammed to see the new conductor plate.
However, I found about this place https://circuitboardmedics.com/mercedes-benz-control-module-repairs/
Who will fix a 722.9 (2004+) transmission. I've contacted them if they'll do the earlier one for my 1999.

I figure it's at least worth taking the plate out and seeing if there's something I can clean or re-solder.
 

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Registered 2002 R170 SLK V8 5.0
Joined
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2,593 Posts
Hi,

Thing is this, no R170 uses 722.9xx Trans, it has 722.6xx, so the conductor plate is NOT a Theft Relevant Part, does not contain an ECU module therefore no programming needed, just good practice to reset TCU Codes and Adaptives with SDS after doing the job :wink:

If it was "Circuit Board Medics" that told you you have a 722.9xx then I would avoid them or whoever like the plague !!

Don't try to repair it, just change the Conductor Plate, they are not expensive :wink:

HTH Cheers Dave
 

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Premium Member 1996 SLK230
Joined
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111 Posts
This winter, my SLK230 went into "limp mode" after starting. As soon as I put it in gear, there would be bump and the transmission would stay in 2nd gear. This turned out to be a ATF fluid overflow. After drawing fluid out with a pump, it ran fine for several months.

Now it's doing it again, but only after warming up. It wants to stay in third gear or above (hard to tell which one). The car will drive fine and then after about 15 minutes will give a lurch. Starting from a stop is sluggish, but driving at 30-40 mph is fine. Last time I tested the fluid levels and came out a bit low, so I added a trickle of fluid.

A test this morning has the same symptoms. Perhaps the fluid level is too low?

However, I'm getting inconsistent results reading my transmission fluid. Whether the transmission is hot or cold, I either read very little fluid, or the whole plastic part is smeared with fluid. I can't tell whether it needs more fluid or not.

The Check Engine light came on for the first time ever, too. When I find my code reader I can give more information.
Fluid type and level are critical
https://www.pelicanparts.com/techarticles/Mercedes-SLK230/70-TRANS-Automatic_Transmission_Fluid_Flush_Filter_Change/70-TRANS-Automatic_Transmission_Fluid_Flush_Filter_Change.htm

The above link is very informative and helpful, apologies if you are already aware.

.

I have changed the conductor plate on my R170 as a precaution as my car has done 150,000 miles, It can be done with the car on axle stands, just be careful when lowering the sump pan as there will be roughly 1/2 litre still in the pan, can be messy :wink::frown:

HTH :tu:
 

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Premium Member 1996 SLK230
Joined
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111 Posts
Circa £1280.

Guesstimate 2hrs labour plus typical dealer charge to clear codes (they do that) roughly £400.
So, parts circa £900.
I know nowt, but that sounds dear.
I agree :tu: as a fairly accurate estimate my conductor plate, fluid 7ltr, filter, gasket, dipstick and plug socket circa 220 GBP.

:grin::Beer:
 

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Registered 1999 SLK230
Joined
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68 Posts
Discussion Starter #16
Hi,

Thing is this, no R170 uses 722.9xx Trans, it has 722.6xx, so the conductor plate is NOT a Theft Relevant Part, does not contain an ECU module therefore no programming needed, just good practice to reset TCU Codes and Adaptives with SDS after doing the job :wink:

If it was "Circuit Board Medics" that told you you have a 722.9xx then I would avoid them or whoever like the plague !!

HTH Cheers Dave
OHHhhhh! No, every search I did on this forum for "conductor plate" gave a result for a R171, which mentioned the anti-theft version. That lead to the wrongful assumption that this anti-theft was present on my R170, and my confusion as to why the service was only offered for the 722.9 and not for the earlier 722.6

That's great news! I can just buy the part and stick it in!
 

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Registered 2002 R170 SLK V8 5.0
Joined
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2,593 Posts
Hi,

Yup !!

Without wishing to confuse you, just lets say you will need to erase the Fault Codes once done, that is the proper way with any fault that has put a light on or caused a limp mode condition .......................

In reality you might get away without doing it, it may drive fine, but codes will remain stored.

If it remains in Limp, don't despair, it likely means it just needs reset :wink:

HTH, Cheers Dave
 

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Registered 2002 R170 SLK V8 5.0
Joined
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2,593 Posts
Hi,

BTW, I forgot to say .....................

When you take all the solenoids out, lay them out in order, some are different to the others, and also carefully remove the little filter screens under the ones that have them, and clean in Brake Cleaner or a little Petrol before replacing them.

Keeping the Solenoids in order will preserve the Adaptive Learn numbers in TCU, although these can be reset with SDS,which I actually recommend after this job, as well as the Code reset :wink:

HTH, Cheers Dave
 

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Registered 1999 SLK230
Joined
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68 Posts
Discussion Starter #19
Hi,

BTW, I forgot to say .....................

When you take all the solenoids out, lay them out in order, some are different to the others, and also carefully remove the little filter screens under the ones that have them, and clean in Brake Cleaner or a little Petrol before replacing them.

Keeping the Solenoids in order will preserve the Adaptive Learn numbers in TCU, although these can be reset with SDS,which I actually recommend after this job, as well as the Code reset :wink:

HTH, Cheers Dave

Thanks for the heads up! I borrowed a code reader from a neighbor, so I'll clear those codes.
Since the 722.6 is used in Jeep, Dodge, and other cars, suppose the local non-mercedes mechanics would have access to SDS?
 
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