What is this broken sensor on the bottom of my Smart ForTwo 451? (knock sensor)

1239 Views 5 Replies 3 Participants Last post by dj.judd, 2 mo ago

dj.judd

Discussion Starter · 3 mo ago

Hello,
I was taking a peak under my 451 today to see if the flex pipe on the exhaust had a hole in it (turns out it doesn't, it's just generally loud). Anyways, as I was looking, lo and behold a broken wire was staring me in the face coming from sort of sensor. It looks like the wire loom that it was connected to is just about 3" away as well. I'm not sure if this is on the transmission or engine, but I need help identifying what I'm looking at. I'd like to solder a new connection or get a replacement and get it fixed. Any help would be greatly appreciated.

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jwight

· #2 · 3 mo ago

One way to tell is remove it and find the part number. Just a guess on my part, but it may be the knock sensor: 2008 SMART FORTWO 1000cc L3 Knock / Detonation Sensor | RockAuto

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dj.judd

Discussion Starter · #3 · 2 mo ago

Brilliant. I always forget that cars have part numbers on everything. I was too lazy to get under the car again since it's getting cold, but I did a lot of googling and can confirm that it is indeed the knock sensor. It should also have 2 wires going to it. Blue and Yellow.

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colin25

· #4 · 2 mo ago (Edited)

You have to watch the engine wiring on the 451, as it is kept under tension (ie, not much slack) and vibration of the engine can disconnect wiring or connectors.

I had the 451 Cdi (DPF model) and there was one wire that hung right under the engine, and could easily be ripped off if something like a tree branch went under the car and caught in the cable loop. I had to try and tie it up out the way. Never seen wiring so haphazardly laid out and fixed.

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jwight

· #5 · 2 mo ago

Thanks for the photo!

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dj.judd

Discussion Starter · #6 · 2 mo ago

Thank you for pointing me in the right direction!

For anyone looking at this thread in the future, I ordered a new connector from Ebay. The original sensor still looks intact, so I'm going to start small and only replace the sensor if it's not working.

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