BMW: O2 Sensor, bmw dealer, oxygen sensor

Question
I have a 1995 525i, US Specs, with 102597 miles.  I'm stationed in the UK and take my car to a local BMW dealer for service.  In March, they replaced the O2 sensor.  Recently, the Check Engine light came on like it did before, so I took the car back to the same BMW dealer  service.  Their diagnostic report is "fault stored with oxygen sensor."  My first question is whether there are more than one O2 sensor on this model.  Second, it seems there is a lot of condensation in the exhaust, is this normal? The car is sound, and runs well.

Answer
Teresa,
 Unfortunately I'm not too familiar with the 5-series, but they should use the same engine and electronics as the 3 series.

 My friend has a 1994 325i, and it only had one 02 sensor.  This car uses the same engine as yours.  Some later models use 2, and some use 4!  You can go to www.bavauto.com and they will tell you how many you need.  
 Some are pricey, so make sure you order the right ammount.  

 Hope this helps!
 Josh