1993 civic lx sedan
Speedometer most of the time sits at zero regardless of actual speed. sometimes it will jump up to the real speed for a bit but eventually it drops again. i replaced the vss and the problem is not fixed. i reviewed the wiring diagrams. at the vss under the hood we have gnd - ignition12v - and the signal wire. ground has perfect continuity with the batt neg post. the ignition 12 v reads 12+ with the ignition on.

here's the strange part, the signal wire (pin 3, yel/wht) reads a steady 4.99 volts weather it's plugged into the sensor or not, weather the wheels are turning or not.

can someone test their plug, specifically pin 3, yellow with white trace, and record the results? preferably with the front jacked up and in gear. alldata says voltage should jump around between 0 and 5 volts.

 

Sorry for such a late reply but I've been diagnosing this week for this same EXACT issue with the EXACT SAME values. What was it ? Did u ever get it fixed ? Or does anyone else have any clue what's the conclusion to this ? Been testing wires all day long and can't seem to find the issue and also checked diagrams.... Still nothing..

 

The VSS produces a 5v square wave. If it's 3 wire, one will likely be 5V always hot, one a ground and one the pulse wire.

If you have replaced the VSS like the old OP, then the problem is more likely the board behind the speedo, they are known to act up after 20+ years. My speedo is from a 93 and is starting the flakiness. I've just been to lazy to pull my bezel off being I screw up and put two clips under the tabs and I'm likely to brake the clips getting it off. Getting to the board on the speedo is really easy and on the 5th gen is only 3 screws holding it the speedo to the gauge cluster. Then another two or three holding the board to the speedo and odometer.

I noticed when it acts up I can smack the plastic front cover and it usually settles out for awhile.

 

never mind I fixed it... Inspected my vss plug and seen corrosion so went to radio shack and bought electronic cleaner spray and sprayed and cleaned with wire brush... Good as new 👍😉✊

 

Very common issue with corrosion on the VSS for anyone in the future reading this post.