Engine swap question

I just put in a 99 (according to the block) 4.0 into my 95 xj. I swapped the sensors and intake manifold from the 95 to 99 (power steering bracket bolt holes were different). What I did notice is that my old block has what appears to be a temp sensor on the back top of the head by the valve cover and also one in the thermostat housing. The 99 didn't have the one on the block. Any suggestions? The one on that head is a little 1 wire sucker that actually snapped off. Do I need this sensor?

Thanks.

That is the sender for the temperature gauge. It was eliminated from the OBDII/1996+ heads, with the ECM temperature sensor being shared for the gauge. You don't 'need' it but your temperature gauge/light won't work without it.

The best place I found to install on my '99 engine was to drill and tap a hole in the flat spot on the thermostat housing. This puts it right next to the ECM temperature sensor.



Later I pulled a few feet of the sender wire from the junkyard, and ran it under the loom cover. Looks factory now.

Appreciate it. Is there any specific sender I need to get? The one on the back of the head has a funky plug on it but yours is just a plain post.