P0140 - 02 sensor no activity detected?

[s14dk]

Hey guys, so i've been dealing with this engine light for a couple of months now and cant seem to figure it out.

The code is P0140 (Bank 1 Sensor 2 after cat) which indicated "oxygen sensor, no activity detected" meaning the 02 sensor is showing ZERO activity with no fluctuation of power at all. Yes I have changed it out twice with Bosch kind thinking it would be the 02 sensor but this was not the case.

When I plug in my chinese BMW scanner the Oxygen sensor is completely dead showing "0" volts. All other sensors are working fine.

I've also: Inspected the Disa valve, cleaned MAF, inspect rubber boots, vacuum hoses, plugs and I still cant get this 02 sensor to come alive!


What are your thoughts??

All help would be appreciated.

[80stech]

Sounds like a problem with the wiring. Try checking the scanner voltage with sensor unplugged.

[PZ06]

visually check and with voltmeter check for continuity the other end of the harness you might have a ripped wire.

[s14dk]

the harness that connects into the o2 sensor reads a solid and constant 12v. So that means the 02 sensor is getting power but the sensor itself is shutting off due to a very lean mixture.. but you'd think it would at least show 0.1 volts ...

[upallnight]

Originally Posted by s14dk

the harness that connects into the o2 sensor reads a solid and constant 12v. So that means the 02 sensor is getting power but the sensor itself is shutting off due to a very lean mixture.. but you'd think it would at least show 0.1 volts ...

That 12 volts could be the 02 sensor heater circuit that you are measuring and not the voltage signal from the 02 sensor.

[Scott ZHP]

Did you coat or wrap the threads with anything when installing it?

[s14dk]

Originally Posted by Scott ZHP

Did you coat or wrap the threads with anything when installing it?

they came pre coated with anti seize


Up all night:

I will look into the harness now. I was reading on another thread how you have the measure the resistance of the 2 white wires and they should be in between 2-3 ohms

correct me if i am wrong

[upallnight]

If you know anything about 02 sensors, you will know that the 02 sensor generates the voltage based on the exhaust heat mixing with the precious metal inside the 02 sensor. Since you replace the 02 sensor twice (hopefully they were new 02 sensors) the only thing left is that one of the signal wire is broken.

[s14dk]

Originally Posted by upallnight

If you know anything about 02 sensors, you will know that the 02 sensor generates the voltage based on the exhaust heat mixing with the precious metal inside the 02 sensor. Since you replace the 02 sensor twice (hopefully they were new 02 sensors) the only thing left is that one of the signal wire is broken.

thanks for the info. greatly appreciated.

so when i test the oxygen sensor itself , should I be looking for voltage or resistance?

and when i test the factory harness that connects into the oxygen sensor what type of reading should i expect?


sorry for the newb questions.

[s14dk]

Do our e53's have a heater circuit fuse for the 02's?