Transmission Adaptation Issues, Limp mode

Andrew Diagnostician Michigan Posted   Latest  
Resolved
Driveability
Drivetrain
2002 Mercedes-Benz S500 5.0L (113.960) 5-spd (722.6)
Transmission Adaptation

Hey Gurus,

I have encountered a vehicle the is throwing me a for a loop and just want to ask a couple questions. This Benz came into our shop with a few major issues of which most have been resolved. The issue I am dealing with now is related to the transmission. It came with many communication errors with the transmission. I completed a full vehicle scan and verified there to be no communication. I removed the connectors and the transmission control module and found there to be a circuit board half way up the control unit and just a pile of rust in the remaining cavity of the control unit. The fuse panel cover was missing and the vehicle sat for a while. NOT GOOD for one of these at all as I'm sure most of you all know. I checked around for the options i could have when dealing with this issue and found that it would be possible to replace the unit with a used component due to the fact that there was no SCN coding or programming specified to Immobilization of this vehicle. We weighed the options with the customer and the cost difference was $150 used vs. $1500 new and actually not available.

Collectively we decide to go the cheaper route. The vehicle will communicate and drive now but after about 5 minutes of driving it will set a Gear slippage fault. The vehicle does no slip according to the data on the scan tool that I can see but I might not be looking exactly where I should be. After about 5 minutes the vehicle will jump back into limp mode (3rd gear) until the next key cycle in which this process will start right over. I did notice an issue with this vehicle as well which is that is has one tire that is a 255/40/19 on the LF vs all the others that are 245/35/19. I am not sure if this would affect the vehicles ability to adapt the transmission either. I am not trying to assume anything at this point anymore. I believe the transmission is solid by the way it drive initially but would like to know if anyone has run into something like this before.

Thanks

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Jared Diagnostician
Maryland
Jared
 

I feel like if it were tires, it would set DTC quicker than 5 min. Is fluid level full? What is its condition? Ive had faulty speed sensor circuits built on the bus plates set false dtc's before. Is it around the same gear commanded gear before going into limp, or random?

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Martha Technician
California
Martha
 

Specific code would be helpful. Also check adaption values to see if transmission has met the limit max values, indication of worn transmission. See attachments.

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Helpful
Andrew Diagnostician
Michigan
Andrew
 

Sorry for the Late reply, The Code is P2502 gear monitoring implausible.

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Edward Instructor
Florida
Edward
 

Do you have an esp light come on when this happens? Tire difference will definitely cause the symptoms you’re describing especially that it doesn’t happen immediately. Years ago I had a 220 with worn tires that did the same thing. If you measure the circumference of the tires you’ll see a big difference.

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Jared Diagnostician
Maryland
Jared
 

I had been thinking about this post... I had a Chrysler with a NAG1 that the customer, armed with a Diablo type programmer, unknowing altered the rear differential ratio in the TCM and caused a symptom similar to what you are describing. This car would set p0730 going around the block. Is there a chance that your used module is programmed for a different rear ratio?

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Andrew Diagnostician
Michigan
Andrew Update
 

Well At this point it looks like we are going install a re-manufactured unit from the dealer which was much cheaper than we expected running at only around $425. This is much cheaper than the original sticker price of a new unit. I will update when we get the unit back and install it.

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Update Ð Awarded
Andrew Diagnostician
Michigan
Andrew Resolution
 

Well This one is down as fixed. We received the Re manufactured unit today. I installed it and took it for a drive. I found the vehicle to shift through all the gears and the Transmission adaptation numbers would change and adapt. I have found that it is safe to say that a re manufactured unit is a plug and play unit. It was ordered according to the VIN. I'm not sure if its coded at the parts…

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