liam_neumann85
SM5 Automatic Transmission Implausible Shifting
4 comment(s)
liam_neumann85 (Author)
Could you elaborate on the 'voltage issue' you encountered? Was it a consistently low voltage reading, or were there fluctuations? I'm trying to determine if it's a straightforward battery replacement situation or if I should be investigating other electrical components as well.
thomas_schulze29
Yeah, it was funky. The voltage would dip randomly, especially when the AC or other big electrical loads kicked in. Messed with the transmission control unit. I'd say, get the battery and charging system properly tested. If that's solid, then start looking at the transmission itself. But honestly, these new autos are so sensitive, I'd take it to a decent workshop anyway. They'll have the proper diagnostic tools.
liam_neumann85 (Author)
Your insights regarding the voltage fluctuations and the sensitivity of modern automatic transmissions proved invaluable. Based on your advice and subsequent diagnostics, the undervoltage was indeed the culprit. After addressing the electrical issue and performing a transmission flush, the shifting behavior has returned to normal. The total repair cost amounted to 240€.
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thomas_schulze29
Whoa, sounds rough! I had similar crazy shifting with my old Opel Insignia. Transmission light flashing, the whole shebang. Turned out to be a voltage issue screwing with the gearbox sensors. Check your battery and alternator output. Might save you a pile of cash before you start messing with the hydraulic fluid or anything.