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Discussion Starter · #1 ·
I think I have read all the posts on this subject here. But they all seem to be at least 5 years old or more.

I have a 2013 that I'm just starting to tow. If I go through the tow procedure exactly from the manual, after connecting the battery again it goes through a transmission relearn or something (sounds like a bunch of clicking). Sometimes I even get a check engine light. If I don't disconnect the battery, everything is fine.

I read an old post (2012) from "Libero" and he says, "It seems to me that the reason for the battery disconnect is to ensure the key does not inadvertently get into the "run" mode (position 1) while towing or the transmission does not move from neutral." He made a lock plate that ensures the key won't turn and it won't go into "D". I kind of think that makes sense. So, I made a lock plate too, except mine is made from plastic. I removed the "fob" from the key part. See pics.

I guess I just don't like all the trans relearning and occasional check engine light after re-connecting the battery. I've done a short test tow with just the locking plate and left the battery connected and all seemed ok.

My question is, would you be comfortable using a locking device like this to lock the key and shifter? And not use a battery disconnect switch? With the lock, the key can't turn on and the shifter can't be moved to "D".

Thanks.
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What about reverse gear? I use the battery disconnect for safety reasons to not take the chance to destroy the transmission. I have flat towed for over 28K miles behind my MH using the battery disconnect.
 

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I also disconnect when flat towing. I have a disconnect solenoid near the battery, and a switch located inside the service flap. Never had a problem, why take a chance?
 

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Discussion Starter · #5 ·
What about reverse gear? I use the battery disconnect for safety reasons to not take the chance to destroy the transmission. I have flat towed for over 28K miles behind my MH using the battery disconnect.
The shifter won't go back into reverse or park without depressing the button at the top of the shifter. What year is your Smart? Does it always do a trans relearn after connecting the battery again, or ever get a check engine light? Thank you for the feedback.
 

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Discussion Starter · #6 ·
I also disconnect when flat towing. I have a disconnect solenoid near the battery, and a switch located inside the service flap. Never had a problem, why take a chance?
Does yours always do a trans relearn after connecting the battery again, or ever get a check engine light? Thank you for the feedback.
 

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I have never had a CEL after towing. The smart car seems to be smart enough to figure things out. Doubtless it must "relearn" some things, but it has never been a problem. I recommend taking the time to wire the taillights into the tow plug harness using the special diodes made for the purpose. BTW, the reason I have the battery solenoid remote switch under the service flap is that you can use a second key to lock the car, then turn off the power. I didn't like having to tow the car unlocked with a key in the ignition. I can provide the part numbers of everything I used for my entire towing setup, if it would help. 🤠
 

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Discussion Starter · #9 ·
I have never had a CEL after towing. The smart car seems to be smart enough to figure things out. Doubtless it must "relearn" some things, but it has never been a problem. I recommend taking the time to wire the taillights into the tow plug harness using the special diodes made for the purpose. BTW, the reason I have the battery solenoid remote switch under the service flap is that you can use a second key to lock the car, then turn off the power. I didn't like having to tow the car unlocked with a key in the ignition. I can provide the part numbers of everything I used for my entire towing setup, if it would help. 🤠
Thank you misfitsailor! I did wire the taillights as you mention with diodes. They work perfectly. :) I have ordered the parts to install a battery cutoff switch under the dash. I've only test towed it a couple times. I had been just removing the battery cable to try things out. But that's a pain. LOL... Thank you for your feedback, I appreciate it.
 

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Why not just put the Smart car on a small trailer? they are quite cheap secondhand, and no need to modify with a tow A frame, or change electrics, or disconnect battery, or having the road wheels turning on the Smart etc. Here in the UK we see a lot of Smart cars being towed on a trailer behind a motorhome. (RV as you say in the states).
 

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I looked into getting a smart car trailer, but there are problems with carrying your car instead of towing it four-down when camping. If you camp at RV parks you will find that many insist that you store your trailer in a special lot, away from your campsite. That's a deal breaker for some of us. It's more hassle to unload the car, then park and unhook the trailer before you can park and start your campsite setup. Also, many public campgrounds barely give you enough room for the motorhome and a car. There is often not enough space to leave a car or trailer attached, and no good place to store it. It's so much easier when you flat tow, you just unhook the car, and you are done. This is my own experience. I think that the trailers are dandy, but I consider them a less versatile option when camping in the USA.
 

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I always disconnect the battery when towing my 453. The only thing I have to reprogram is the clock and the radio preset stations (which I don't use anyway).
 
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