1995 coupe 48,500 miles. Month ago check engine light on but no sys light. Jump 4&12 on obd2 gives H13 code only, drivers side o2 sensor. Also after check engine light comes on both cooling fans run even though temp at 200 degrees or less. I changed out o2 sensor. Light and code and fans on again. Checked battery and it is good. Car was not idling bad or running rough when light came on. I thought the H meant historic code, so maybe not o2 sensor, as I changed it out once before some time ago. Maybe unrelated but PKE fob working sporadically.  Does this ring a bell with anybody ?

Well I changed out the ebay bargain o2 sensor with a denzo brand. No check engine light and no codes.

Get them all the time that may or may not work properly...it's a crap shoot most of the time. Good to hear it's working well now.

I have a 1993 did not have an H 13 code until I changed the 02 sensor. Once I had the 13 code I checked as to why you could have this problem. Connection getting hot or oil possible on the connection. Upon inspection the connection was hanging close to the Cat converter that gets very hot, so I re adjusted the connection using the factory clips located on the frame. I also cleaned a little oil that was on the wired female portion of the connection. If not used the vehicle will leak a small amount of oil in the back of the motor. Seal must contract, this oil over time drips onto the 02 sensor wiring. Oil does not leak when frequently used due to the seal expanding and there is no loss of oil on the dipstick, leakage is minimal as to there are no spots on the floor of my garage. Now If I did not run the car for a year or longer there may be a spot on the floor. Once I cleaned and adjusted the location of the 02 sensor and reset the codes no problems other than a 44 code that I cannot correct since last year.