722.6 Trans P2502 fault code - Mercedes Forum - Mercedes Benz Enthusiast Forums

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Old 01-02-2017, 11:37 AM
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Default 722.6 Trans P2502 fault code

2001 S430. 722.6 Transmission went into limp home mode. Checked codes with iCarsoft MBII OBDII. Codes suggested and I replaced the Electronic Plate on the Transmission Valve Body as well as the Electrical Conductor which was dry of any leaking fluid. While I had it out, I cleaned the selonoids and tested them within correct ohms and clicking under 12 volt power. Cleaned valve body within a meticulously clean and lint free environment. I did not do a valve rebuild of the valve body but all appeared clean and good with no scarring. Transmission Oil Pan was a bit mucky and in need of an oil change but no debris within the oil pan or the valve body and selonoid filters. Reassembled. Fresh Transmission Fluid and Filter. Codes cleared. Operated perfectly for the day of starts, stops, up mountain driving, down mountain driving, shutting off engine, restarting engine... all worked perfectly... until a 3 mile drive on the interstate at 70mph. All seemed to upshift perfectly onto highway speeds, and downshift smoothly upon exit. At next redlight the vehicle shifted hard into first gear... then limp home mode again. I am throwing one single fault code for the transmission of P2502 (implausible gear or transmission slipping). I can clear the code and vehicle will shift into R or D successfully with a slight delay. Reverse works perfectly, but immediately as the vehicle moves forward and should shift from first to second I get the P2502 code again. This occurs the same in Winter mode or Summer mode (starting in 1rst or 2cd gear), whether moving downhill with no pressure on transmission, uphill with pressure on transmission, or on level ground with normal slight pressure on transmission. Checking the live data feed with the MBII tool it appears that the torque converter and lock up clutch are at least working appropriately up to the point of throwing a P2502 code. My limited knowledge would seem to indicate a torque converter problem, but my Indy Merc shop seems to think I have another bad Transmission Control Module, as code thrown does not vary between W and S trans settins. I can find no one else experiencing a single solitary P2502 code in limp home mode. Everyone else finds multiple codes with the P2502 code which lends clues to the source of their problem. ---anyone else have experience with a single P2502 code or solution? Any suggestions appreciated before I begin replacing parts associated with the P2502 one at a time to find the solution.
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722.6, limp home mode, p2502, s430, tcm

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