O2 sensor heater question

I had this code come up on my wifes 01 Grand, and changed it, no problem.
Yesterday, on my 2000 XJ, I got a check engine light. 4 codes came up, all 4 O2 sensor heaters. I cleared the codes, and they came up again immediately.
It seems like a longshot that they all went together, I checked the fuses and relays, and there are two relays for the O2 sensors , but I didn't see one for the heaters?
Has anyone else had this happen? Is there a fuse or relay for the heaters?

There is a fuse in the power distribution block under the hood. Can't remember the fuse number, but on my 98' it was not very obvious/ not labled as O2 Heater or anything like that.

Was it one of those mini fuses in the middle? The underside of the cover has a schematic of the relays and big fuses, but it just shows the amps for the mini's...

I pulled up the schematic.

Looks like Fuse 17 provides power to the O2 Sensors. The Fuse is before the relays in the PDC.

On your wife's WJ Grand, there's a PCM software update. On your XJ it's the yellowish 20A Fuse #17 in the underhood fuse panel (PDC).

Thanks for your help guys, I'll try it tonight.