AHZELA

P0702 woes

28 posts in this topic

OK so the car has been pretty good since coming out of retirement a few weeks back. I really haven't had an issue with the little guy till recently.

 

    Other day im driving along.. and I get a funny shift from 1st to 2nd with a blank screen...  It was an anomaly and i figured nothing of it. Then yesterday I get to a job site.. park, and go about my morning. Someone asked me to move the smart, and when i looked to shift into R .. I got the blank screen again. No bars.. just blank. So I open the door, shut it off, turn the key and I can here the actuator sounding like its trying to pull itself back in to no avail. after a few clicks it stops... blank screen.. I cant get it to N, or R, or 1...  the actuator wont move. My thought at this point is the hole is a bit worn and its stuck.   Get a jack... and some QuickSteel  pop the actuator off.. (as well as disconnect electrically) fill the hole and leave it for the day.  End of the day.. starts up.. and I drive off without issue.

 

    About an hour later as I get home and goto back into my spot... no R again..  again the actuator making all kinds of noise, and a blank screen.  So now this isnt making sense, its not the actuator stuck in the clutchfork..  I seem to be able to get it into 1st so I drive around the lot and get into my spot nose first. Check for codes and I have p0702.

 

      So if it goes into 1st... but not R, is this going to be a wire/connector issue? Or something else?   I have replaced the gear position sensor a couple years ago.. and this is a used actuator I picked up also a few years ago... but I dont feel like the actuator is the prob.

 

Thoughts???

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my guesses

 

#1 actuator problems

 

#2  transmission position sensor wires/connector issue

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My guess - actuator. The motor or gearing in these can fail.

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Posted (edited) · Report post

10 hours ago, smart142 said:

My guess - actuator. The motor or gearing in these can fail.

 

   Anyway to test or verify this before I drop $600 on a part? I thought days of replacing expensive parts ended with me parking the truck! lol!!   Also.. why does it go into 1st but not into R if the actuator is in fact at fault?

 

I have another actuator, but the collar broke that holds the rod, Can I swap the motor in the actuator??  I guess I can open it up to look at the gear..

 

 

   QUICK UPDATE   I just went out, and with the key on, engine off I can shift from N to 1 to R.. I hear very quick movement on the actuator and the number shows on screen.     With the engine running not the same... it will go from N to 1 but when going to R i get a blank screen. After that it wont shift to anything.  I did see a 6 and a downshift arrow in the sequence somewhere as well  When I shut the engine off.. and look for a gear, I can hear the actuator going in and out a few times...  It wont find a gear at this point and a series of key off... on.. shift etc will get it back to N.

 

   Is it under load that its having the issue??  Maybe it is the actuator...

Edited by AHZELA

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You need to get a STAR  to look at it....a re-teach of actuator and tranny....maybe that will help? Before buying hardware.

If you are careful and patient the actuator comes apart for cleaning or peeking and probing....also maybe fixing...lol.  It is held together with rivets, the backing plate that is....but it could be epoxied back in place and then sealed up water tight with a drain hole in the correct location. Re-riveting the plate back on nicely is a serious pain...but can be done. You'll need very small rivets. I used both rivets and silicon, your favorite sealant...lol.

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i dont have any idea why it would show a 6 just sitting there 

 

that makes me lean more to a confused actuator due to signal problems from gear sensor/transmission position sensor

 

 

if the sensor is showing wrong gears the actuator doesnt know what to do

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24 minutes ago, LooseLugNuts said:

i dont have any idea why it would show a 6 just sitting there 

 

that makes me lean more to a confused actuator due to signal problems from gear sensor/transmission position sensor

 

 

if the sensor is showing wrong gears the actuator doesnt know what to do

Hence the tranny reteach....maybe..?   Just a thought?

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take the actuator apart and have a look see.  the electric motor is only held on with screws.  when you take the motor off you will have a clear view of how the electric motor engages the drive.

on one of mine i could clearly see that the motor gear was fine,  but the arm it engaged with (that moves the rod) was stripped.  it looks like it might only be made with plastic.

 

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Could be the clutch dragging if it works fine with the engine off but not when running.

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18 hours ago, mender said:

Could be the clutch dragging if it works fine with the engine off but not when running.

 

 

   ... I feel like this is something I would have felt coming no? There have been zero issues shifting etc.. This just came out of nowhere.  

 

I am going to get a look at the actuator, as well as a possible re-teach and adjustment over the weekend.

 

When the freezing goes away.

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Posted (edited) · Report post

I'm an AST but haven't worked on Smarts before, so I don't have a history to draw from on these. It might be as simple as an intermittent brake pedal switch but it'll be interesting to find out what is causing the issue.

 

However, the symptoms are what I would expect with a dragging clutch, which I do have experience diagnosing and fixing.

 

You said earlier that you could hear noise from the actuator when it was trying to shift with the engine running; how did that compare to the sound with the engine off?

Edited by mender

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I was able to get ahold of a STAR..  

 

   When I try to run the 3 actuator tests its says you have to turn the key off.. then back on. Most times when I do that It goes into a blank screen, or 3 bars.  I have seen the word "fault" come up in the teach section after said tests.  

 

  So I am guessing it wont even teach?? Or is there something i am missing. Is the teach in the test section or somewhere else?  I don't have a ton of XP using this system.

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Posted (edited) · Report post

OK!

 

   So I was able to figure out the teach, and it seems to have worked. Also...  the recent "quik-Steel" fix from the other week did not stick. So i am sure the fact that it was moving around in the fork caused some confusion for the actuator. I need a better fix for the rod, and another teach and I think I will be good.

 

  EDIT!!  -   Drove for 15min, shifts nicely.. get home and goto R and I get a blank screen. Have to shut the car off and start it again, I can do 1st and 2nd etc.. but it wont go into R.   Shifter motor??

 

Now.. while I have this Machine... is there anything else I should take care of??   Can I diagnose how much clutch is left etc...???

Edited by AHZELA
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It can do so much if you can find out where all the sections are....I have spent countless hours searching my way through to find out all the different things it can do....The hard part is remembering how you got to where you are....lol.  Yes it can figure out the wear but it also needs to get it's position correct as a base point....and if your actuator isn't adjusting correctly it can't find that starting point...I don't think? I could be wrong. You can find out compression rates, the balance of the engine, fuel pressures...Much more....I'm not the best guy to tell you exactly what it can do......so really shouldn't be commenting...but if you have the STAR to use for a time have at it....keep searching within the program. Like I said, i have literally spend days searching within it.

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Some guys here have found an acorn nut to fit over the end of the actuator.  It’s diameter is larger than the hole in the fork so will work for some time.  I think Glenn had someone machine some domed caps to fit the end of the actuator and epoxies them on, I have one on mine.  If you have a welder friend maybe it is possible to weld the hole without removing the fork.  I know someone here that might try but I’ll let him speak for himself if he is even interested.

 

Nigel

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Ah, the acorn mod! Bil Gladstone and I did the mod on both our cars awhile back... if I remembered correctly, we got an 1/2" acorn nut, drilled the threads out, and kept the nut at the end of the rod with silicon. Some members reported that the nut would wear out quick, but I never had any issues. The original guy that did this mod was able to find a brass acorn nut.

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I am actually thinking about the sleeve that glen has sorted out.. seams like the easier method. no shaving of the rod, and can probably secure it with epoxy.

 

   I think my issue now is Not actuator related tho.. I have read about software issues causing the no R shift.. but may be only 2008 years?  I am a bit worried tho that this could be a clutch problem. 

 

   Hoping for some more input ...  :rolleyes:

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Just my 2 cents. If the actuator rod punched thru you would have one problem. (the car just would not move) you would also hear a clunking caused by the electric shift motor trying to shift the trans with the clutch still ingaged.

The clutch actuator does just one thing, same as you would if you had a regular standard car, and it was your foot pushing on the clutch pedal. 

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9 minutes ago, Sydney said:

Just my 2 cents. If the actuator rod punched thru you would have one problem. (the car just would not move) you would also hear a clunking caused by the electric shift motor trying to shift the trans with the clutch still ingaged.

The clutch actuator does just one thing, same as you would if you had a regular standard car, and it was your foot pushing on the clutch pedal. 

I agree with this even though I have zero experience with this issue personally.....on this vehicle. IF your rod punched through it wouldn't move the clutch fork anywhere making it impossible to push the clutch to be able to change gear at all.  IF it is partially punched through and it can move it lets say half way where it needs to go it would constantly throw up codes and make shifting almost impossible, no?  IF as some say an acorn shaped attachment added to the end of the actuator rod will work then that would be my choice to try next. They would be easy to turn out on any lathe....especially if you chose to make them out of brass for future wear restrictions on the fork side and use the new acorn  attachment as the sacrificial lamb from now on. You can get brass enfused with oil to help with lube of some sort. Depending on the amount of space in there maybe you could make them with lock nuts to help keep them on shaft or maybe even thread shaft and thread acorn also....that giving you some adjustment for the future.? I haven't looked at the fork yet personally to see how easy it is to weld up the punched hold.....but if I can get my welder to it, I can weld it.  Steel only.....I have a workable mig, a Tig would be even better.

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While I appreciate the discussion around the clutch actuator rod. This is not the issue lol.   

 

However I think trying to weld into the small hole in the trans, into a smaller hole in the clutch fork would be a tricky task.

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Posted (edited) · Report post

Well... with the nice weather today I was able to pull the harness and get a good look. I had 2 breaks.. the main one being at the connector that goes into the transmission. Not the gear position sensor, but its a 2 wire connector. Of course the break is right at the connector. I was able to fix it as a temp solution... but im going to need a pigtail. I know MB sells them, but does anyone maybe have a list of part numbers on the shifter harness pigtails??  

 

  I also need the shifter motor pigtail.

Edited by AHZELA

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2 wire connector I guess is for transmission speed sensor. 

 

For above, for gear change motor and for clutch actuator there are no repair kits available from Smart but there are for other Mercedes models that use same connectors. The problem is how to find these. You will need the services of a very skilled and helpful Mercedes parts person. 

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A complete engine harness costs now more than £300. 

Smart only supply one repair tail (connector with short length of cable) and that is for temperature sensor. Same plug for coolant temperature sensor, inlet air temperature sensor and outside temperature sensor. 

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figure out how to get the metal parts out of connector without damaging....then solder or re-crimp your own pigtail

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