No power to o2!

[GoochE30]

Hey guys,

Tested the wires to my o2 and none of them have voltage when they should.. What is happening that would cause that? Ecu problem? 1987 325i

[Mill-ix]

The o2 sensor should be getting 12 volts of power whenever the key is turned to the run or start position, the battery provides power to fuse 9 which provides power to the o2 sensor heater relay which gives 12 volts to the 02 sensor.


Check fuse 9 first, then check for 12 volts at the heater relay, you could check for continuity at pin 16 on the diagnostic connector since this connector is before the relay in the circuit.

http://www.armchair.mb.ca/~dave/BMW/e30/

Page number 1360-6 and 1360-7 shows the diagram for the heater relay to the o2 sensor.