Does any know how to test a 5 wire o2 sensor (maybe in Bentley manual) for a 528xi 2008. I have 105000 mile's, so i wanna rule out bad wiring or faulty sensor. Also does anyone know where i can purchase a cheap OEM sensor, for bank 1 sensor 1 (bmw# 11787558055). I have checked via ODB2 and the bank2 sensor 1 is running at 780 Celsius, while bank 1 sensor 1 is at 580 degrees Celsius (this sensor is throwing the code).

Anyway to test the sensor or wiring harness?
And where can i buy cheapest sensor?

 

I bought 2 pre-cat O2 sensors for $216 in July last year from Amazon. That's the lowest price I found for Bosch OEM O2 sensors.

I don't know a reliable way of testing the O2 sensor without scope.

 

Did you also have P0135? or a heater code for the o2? Also, i only have 1 o2 code should i replace both?

 

I replaced O2 sensors as a preventive maintenance; didn't have any codes/check-engine-light. My car had 135K miles when I replaced the O2 sensors.

If I were you, I'd replace both sensors. If one is giving error code, the other one is not too far away from failing.