siegfried_weiss8
Automatic Transmission Problems on Mercedes ML
Summary of the thread
A 2015 Mercedes ML is experiencing automatic transmission issues, including slipping, a transmission indicator light, and improper shifting, suggesting it might be stuck in emergency mode. Potential causes include low or contaminated hydraulic fluid and electrical system issues, particularly undervoltage affecting the transmission control module. It is recommended to check the battery's condition and have a qualified technician perform a diagnostic assessment to identify and resolve the problem. The issue was ultimately traced to undervoltage, which was resolved by addressing the electrical problem and clearing the fault codes, eliminating the transmission slipping.
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4 comment(s)
siegfried_weiss8 (community.author)
Undervoltage, huh? Interesting. I haven't checked the battery specifically, but the car starts fine. Could that still be the culprit even if it starts okay? What's the connection between the electrical system and the automatic transmission acting up?
lisamoon1
Indeed, even with adequate starting power, a marginal battery can present issues. Modern vehicle systems, including your Mercedes-Benz's automatic transmission control unit, are highly sensitive to voltage fluctuations. Insufficient voltage can lead to corrupted data transmission and, consequently, the symptoms you observe. The connection is analogous to a chain reaction, wherein a weak link (undervoltage) affects the entire system (transmission control). While I cannot definitively diagnose the issue remotely, given the described symptoms, it would be judicious to present the vehicle to a qualified technician for diagnostic assessment. A diagnostic scan tool should be employed to interrogate the transmission control module for stored fault codes, and the battery's state of charge and health should be evaluated under load.
siegfried_weiss8 (community.author)
Thanks for the advice! Turns out you were spot on. Took it to a workshop and they found undervoltage was the issue. Apparently, it messed with the transmission control unit like you said. They sorted out the electrical problem and cleared the codes. Cost me 240€, but at least the slipping transmission is gone!
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MERCEDES
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ML
lisamoon1
Having reviewed your description, the symptoms you are experiencing suggest a number of potential faults. It would be prudent to ascertain whether the hydraulic fluid level is correct and that the fluid is free from particulate contamination. However, have you had the vehicle's electrical system assessed recently? Specifically, was the battery condition checked? In certain Mercedes-Benz models, undervoltage conditions can induce erratic behavior in the automatic transmission control module, leading to the symptoms you have described. It is a situation akin to a computer glitching due to insufficient power.