romy_sturm57
Peugeot 107 transmission issues
Summary of the thread
A 2013 Peugeot 107 with 150,762 km is experiencing erratic automatic transmission behavior, including unpredictable shifts, refusal to shift, and activation of the transmission indicator light, occasionally entering emergency mode. The issue may be linked to worn-out transmission oil or undervoltage affecting the transmission control unit. Solutions include checking and replacing the transmission oil and addressing any voltage issues, which resolved the problem in this case.
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4 comment(s)
romy_sturm57 (community.author)
Undervoltage, huh? That's interesting. I haven't checked the battery specifically, but the car starts fine every time. Could undervoltage really cause those kinds of transmission problems even if the car starts okay?
bernd_guenther1
Yes, it's quite possible. Modern cars are very sensitive to voltage fluctuations. While the starter motor might have enough juice to crank the engine, the voltage could still be dipping low enough to mess with sensitive electronics like the transmission control module. The TCU relies on stable voltage to properly actuate the solenoids and control the gear shifts. If it's not getting the right voltage, it can cause all sorts of unpredictable behavior. You should get it checked as soon as possible.
romy_sturm57 (community.author)
Thanks a bunch! I really appreciate the insight. I took it to a local workshop, and they confirmed your suspicion. Turns out, undervoltage was indeed the culprit! They replaced the transmission oil, which was pretty worn out, and sorted out the voltage issue. Cost me 240€, but at least it's running smoothly again!
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PEUGEOT
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107
bernd_guenther1
Sounds familiar! I had a similar problem with my Opel Astra a while back. Same implausible shifting, lights on the dash, the works. Initially, I suspected a sensor issue, but the symptoms you're describing, especially the emergency mode, could point to undervoltage causing havoc with the transmission control unit. Has your battery been checked recently?