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Another VSS mystery 99XJ NP231


NAXJA Forum User
AZ 480
So I’ve searched and am still in a quandary. My 99XJ with NP231 started having speedo issues. Speedo/odo will work every ignition until I hit about 50mph then either bounce and drop to zero or just drop to zero.
Throws P0500 code.

I have replaced the VSS, checked pinion gear that drives VSS. Key on I get 5V at supply wire and 5V at sensor wire. Checking ground wire I get .5ohm grounding to transfer case. Instrument cluster passes check and no other gauges affected.

I’m perplexed by why it works initially every start cycle then falls out within a mile and never comes back (I’d think a short would give me intermittent operation while driving/bouncing down road).

Jeep runs and shifts fine, just no speedo.
Plates are due with emissions OBD test next month-I need to get the CEL to be gone and stay gone for 50cycles or I won’t pass.

Any input on this would be highly appreciated.
The P0500 code would suggest a wiring problem.