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Registered 2002 SLK320
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41 Posts
Discussion Starter #1
Hey all, i need a little help with this one. The car is a 02 SLK320 auto.

Last winter i had the car go into limp (2nd gear only, shift display stays black). So i bought a e bay shifter and things started working fine.

6 months later after sitting for a week i get the same problem. One note, it seems if i start the car and rev it to 3000rpm for 30 sec or so it starts to work agein. This revving thing has worked 5-6 times for me.
The problem only starts after sitting 5-6 days.

I checked the battery and it’s strong, starts real easy when this happens.

Wondering if there might be a low voltage problem or something else going on.

Btw, the car runs and shifts flawlessly when not in limp mode...

Thanks in advance Steve
 

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Registered 2002 SLK320
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41 Posts
Discussion Starter #2
Just a update, things are getting worse, seems almost every time i start it she goes into limp.
Rev it up for 20-30 sec and restart and it runs fine.

When I replaced the shifter last time I didn't see a problem with it, wondering if this could be the
contact plate in the trans???

Steve
 

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Registered 2002 SLK320
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1,997 Posts
Hi Steve,

It could be this it could be that ..............

Soooo many things can cause a Limp Mode that to actually almost guarantee getting to the problem first go, and thus avoid wasting money on parts you don't need and valuable spare time, you really need to get the Car read on SDS, not cheaper machines, SDS, and by a decent operator, then we can advise what is wrong :wink:

HTH, Cheers Dave
 

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Premium Member 2005 SLK55 AMG; 2005 SLK350
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4,682 Posts
Agree with the need for a good scan (I am not so dogmatic about SDS vs carsoft vs Autel though).


In the meantime, did you check the pilot bushing (where the wires exit the transmission) for ATF wicking into the wiring harness? And did you check the foam rubber in the footwell - near the grommet allowing the wiring harness through - for any red tint?
 

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Premium Member 2001 SLK200K/2001 SLK320
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1,597 Posts
Could be a leak that's getting worse (any damp patches on the ground under it?), revving up for 30secs or so seems to suggest low fluid that could be warming up to some sort of workable level ... wouldn't hurt to buy a dipstick >:D
 

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Registered 2002 SLK320
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1,997 Posts
Agree with the need for a good scan (I am not so dogmatic about SDS vs carsoft vs Autel though).
Hi @efair ,

No offence intended here, (and I'm sure there wasn't in your post either) :wink: :smile:

I'm not trying to be dogmatic.
There is pages and pages of very good reasons to spend circa £400 on a basic SDS System, not just the ones written by me either, so yes I do plug these machines, simply because myself and others who have made the transition to SDS from lesser machines are not exaggerating claims :wink:

An icarsoft may well tell you that your PSE or TCU is faulty, but it won't be able to Version Code a new or used unit to suit the specific vehicle, many owners have ended up chasing ghost faults because they do not realise these cars (even the aged R170) are as complex as they are ;)

Being a Garage Workshop owner who specialises in Diagnostic and Rectification works, and for the best part of my mid 20's to early forties I owned and ran a successful Auto Trans Rebuilders, I have the luxury of many Dealer Level machines as well as 3 generics, Snap On, Autel and Delphi. These Generics obviously cost way north of the SDS £400, and are very good in their own right.
No one machine does all unless you have the Dealer Level Kit, like SDS for MB's, JLR for Jag Landrover, ISTA INPA etc for BMW, VAG Com for VAG Cars etc etc.

I know for a fact that icarsoft and Autel / Snap On / Delphi and many more do not access more than 80% of Codes and not in all modules.

I have often experienced owners going off on tangents and telling me there "is no fault codes", plug the Car into SDS and wham Fault Codes, Data, Guided Diagnostic, Wiring Diagrams, Part Locations, Part Numbers, Version Coding, Developer etc etc etc all at your fingertips.

These are just a few reasons I advocate using a £400 SDS over any other, simply because it is the correct and very powerful tool for these Cars, and not just a simple diagnostic machine ;)

I'd go so far as to say it is almost essential on later Mercedes models, such as R171 , R172 and also on same vintage as R170 but higher end Cars like W220 S Class C215 CL etc etc

Anyway, like I said, just a discussion of what and why from my own perspective, absolutely no offence intended or taken :wink:

Back to OP ;) ................

I agree this does sound like a low Oil level, but it could also be a bunch of other things and I know for a fact if it were put on SDS I would know exactly where the fault lie in the Transmission System, and whether or not it was worth a rebuild or good used unit time :)

If it had been "read" on anything else one simply cannot be certain, unless it is one of the more common faults.

So first and simplest step, verify the Trans Oil Level and correct if necessary. Check the areas mentioned for leaks, plus look for other leak sources if level is low.

If you need to add Oil, once the level is correct, then test drive and report back if she's driving OK, if so rectify leak, if not we need to go more in depth !!

Final thing to note is that each time you add oil, it clings in the dipstick tube, more so on MB 722.6, so you need to insert and remove/wipe the dipstick a few times each time you add oil in order to get an accurate reading ;)

HTH, Cheers Dave
 

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Premium Member 1999 SLK 5.4 M113
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1,433 Posts
Why do you think it's the shifter?

It is going into soft limp-home mode, which will allow it to be reset every time you restart the car. You got lucky it isn't a hard limp-home condition.

usually soft limp-home is caused by speed sensor or conductor plate issues.
 

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Premium Member 1999 SLK 5.4 M113
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1,433 Posts
What is soft limp mode ? vs hard limp mode ?


Soft limp-home mode resets when you restart the car. it will lock the transmission in 2nd or 3rd. Hard limp-home will lock you in 2nd and it can only be cleared with a snap-on scanner or SDS.. so you should probably fix the problem before that happens!
 

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Registered 2002 SLK320
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41 Posts
Discussion Starter #11
I scanned it with a snap on scanner today, left the code at work p18- - somthing... think it was something like failed some kind of shifter test.
I’ll up date tomorrow.

When i changed the shifter in jan the code pointed right to it, funny thing though the code normally came up when somthing gets spilled in the shifter. The shifter did fix it for 5-6 months, this was a 18 year old ebay shifter.

Also checked the plug coming out of the trans today, yes it was damp with trans oil. 2 of the wires on the bottom of the plug were wet with oil. This “leak” is so small there is no drip. Good idea to get a dip stick though, i get the impression there is a electronic level sensor on the valvebody, can i access it with the scanner?

The reason i’m assuming shifter is the black display when turning the key on, no P just a black screen. Also when the car does show P it works shifts and works fine.

Steve
 

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Premium Member 2005 SLK55 AMG; 2005 SLK350
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4,682 Posts
I would next take 10 minutes to pull back the carpet in passenger footwell, remove the styrofoam, loosen the three plastic 10MM nuts that secure the equipment bridge, and lay the equipment bridge down so you can see where the harness comes through the foam rubber. If you see red stains there, you need to address this leak/wicking first.
 

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Registered 2002 SLK320
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41 Posts
Discussion Starter #13
I would next take 10 minutes to pull back the carpet in passenger footwell, remove the styrofoam, loosen the three plastic 10MM nuts that secure the equipment bridge, and lay the equipment bridge down so you can see where the harness comes through the foam rubber. If you see red stains there, you need to address this leak/wicking first.

Advise taken, peeled the foot well back and checked the harness coming though the tunnel, cut the insulation back and things are dry. BTW, what are
the 2 modules on the plate, ECM or TCM and amplifier?


Codes from yesterday.


Shifter: P1856 "Fault in selector lever test"


Trans: P240C, "Can signal selector level position selector module"
P2313, "can fault n15/5 implausible level position electronic selector module ecm


Engine: P2013 "evap"
P2016 "evap"
P2067 "electronic trans ECU N15/3 (stored in component)
P2030 "electronic selector lever module control module"


A note here, I didn't clear the codes after changing the last shifter or after the evap repaired itself...


Steve
 

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Premium Member 2005 SLK55 AMG; 2005 SLK350
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4,682 Posts
TCU and amplifier - correct.

It sounds like your TCU has failed - no CAN comms with the ECU.
 

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Premium Member 1999 SLK 5.4 M113
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1,433 Posts
I second that, sounds like a TCU issue. Just get one off eBay.. make sure the numbers match!
 

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Registered
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63 Posts
Soft limp-home mode resets when you restart the car. it will lock the transmission in 2nd or 3rd. Hard limp-home will lock you in 2nd and it can only be cleared with a snap-on scanner or SDS.. so you should probably fix the problem before that happens!
Would you mind sending me a link where you read that ?
Mine has been going in limp mode because of the manifold flap problem and I have been able to shift to a higher gear when it is in limp mode. Pull over and restart and I'm back to normal.

 

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Premium Member 1999 SLK 5.4 M113
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1,433 Posts
Would you mind sending me a link where you read that ?
Mine has been going in limp mode because of the manifold flap problem and I have been able to shift to a higher gear when it is in limp mode. Pull over and restart and I'm back to normal.

There are quite a few posts that talk about it, but most of my knowledge is from personal experience. I drove home from 2 hours away in 2nd gear because of Hard limp-home mode. You can throw it into soft limp-home by simply over revving and also exceeding the torque values programmed into the TCU.. both of which I have done with my V8 swap. I have had occasions where it would be in L-H mode, but if you are in a gear higher than 3, it will not shift to 3 until you slow down enough. I have also had scenarios where it will not go into L-H mode until after 3rd gear, which is typically a speed-sensor issue. In those cases, I could just lock it in 3 and still have the first 3 gears, just dont let it shift into 4th.

https://www.benzworld.org/forums/c208-a208-clk-class/2031673-722-6-transmission-hard-limp-home.html

https://mbworld.org/forums/e-class-w210/362359-how-do-i-get-trans-out-limp-mode.html
 

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Registered 2002 SLK320
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41 Posts
Discussion Starter #18
So tcu, one last test.




The car has been working for the last 2 days, the next time it happens
I want to rescan and confirm the same codes are there.


Steve
 

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Registered 2002 SLK320
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1,997 Posts
You can throw it into soft limp-home by simply over revving and also exceeding the torque values programmed into the TCU.. both of which I have done with my V8 swap.
Hi Aaron,

Disclaimer ;) ...... I'm not questioning what you say there /\ /\ /\ !!

I am curious about this, as you know, my intention is to fit the V8 first, and leave the V6 Trans and Diff, so I can be certain that any issues I get will be purely down to ME Version Coding error so .......................

How much throttle do they stand before they notice the Torque is exceeded, (roughly) like 1/2 , 3/4 , only on WOT etc ????

Also, how the hell are they monitoring this ????

I can only assume they detect a slip, or they are doing a complex CAN Comm calculation based on the Torque figure coded into TCU, Torque figure coded into ME and Throttle opening :wink: .....................

Or, (as I often do), am I just over thinking this ????

TIA, Dave
 
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