1999 Civic HX CVT ; 239K miles
Speedometer not working - heard that it is fairly common problem with Honda to have a failed vss.
However, getting confused on which is the correct speed sensor, I keep getting hits for two different kinds. And when I look to my transmission (firewall side), there are two plugs. So do I need to change out both of them??

1. https://www.rockauto.com/en/moreinfo...355611&jsn=780
2. https://www.rockauto.com/en/moreinfo...355611&jsn=777

 

The first one is the CVT input speed sensor. The second one, with the gear on the end, senses road speed and drives the speedometer.

Does the odometer work? If so, the speed sensor is OK. Is the VSS code being thrown along with other codes like O2 heater and purge solenoid? In that case you have a fuse 15 problem. VSS code but no other codes could be the sensor only. Also check that the sensor plug is not corroded. Failure of the sensor itself is not very common.

 

The odometer doesn't work as well whenever the speedometer needle drops to zero. I did look for corrosion and didn't see much. Couldn't locate the contact cleaner otherwise would've sprayed it down. (Also, the problems started after I hosed down the engine bay - so corrosion was also my first thought).
So, I just need the sensor with the gears, right?

 

P0501 is related to the Vehicle Speed Sensor signal, which is the one with the gear.

 

I bought an after-market speed sensor (https://smile.amazon.com/gp/product/B00NI6UPS0/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1) but it turned out to be different even though it was 'compatible' - see pictures. The grooves are in different direction and the sprockets (?) size is different as well.
Right now I am managing as the sensor kicks in intermittently and works fine until next drive. But I wonder what damage it would do long term and how urgently I need to get this fixed??

 

I think you can pull that spring clip out of the side, slide the shafts out and swap the shaft / gear that fits your car into the new sensor.

 

I believe mk378 is right here... just make sure you don't drop the small shaft "key" that fits in the top of the gear shaft and turns the electrical component inside the plastic VSS body.

 

Will give it a shot and let you know. Thanks!

 

So I swapped out the gear shaft between the two and the newer sensor body will not fit all the way into the port. It was too long by about 3 mm.

And yes, I did drop that little piece from the new one....
But the old (original) one had that little piece gummed up and stuck. Sorry did not take pictures. So I cleaned it up with some brake cleaner and pried it out and cleaned some more. It started to move more freely but once I installed it into the vehicle, it was still erratic as before (maybe a little better).
It would not register initially and somewhere during the drive it will kick in. Only thing around this time, when it begins to re-engage, the speedometer needle goes crazy jumping all over the place and in addition, the engine would begin to bog. So yesterday, I ended up unplugging the sensor while I look for the right replacement.
I had found something about a couple of weeks ago which seemed a match, but can't remember now.
If y'all can help me find, I'd appreciate it very much.