E46Fanatics - View Single Post - Very weird auto transmission slipping problem
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Old 08-30-2019, 08:44 AM   #2
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Join Date: Jul 2008
Location: USA
Posts: 9,658
My Ride: 2018 M240i
The first step in diagnosing a problem is to scan the engine computer (DME) and the automatic transmission computer (EGS) with proper software to get all of the codes. Is the transmission a ZF or a GM? The use different fluids. The GM transmission uses Dexron3 while the ZF transmission uses a more exotic fluid. Did you follow the manufacturer’s procedure when filling the transmission? Basically, both under- and over-filling the transmission will cause issues. Did you replace the fluid filter? If you did, what brand did you use? One the transmissions (ZF or GM) has a problem with the wiring harness that needs to be checked and corrected if it’s damaged. Also I think the software in the EGS for the GM transmission was updated do to correct for a fluid pressure issue when the transmission is cold.
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