O2 Sensor Heater Circuit Fault - RESOLVED

iain_Z4C · Post by **iain_Z4C** » Wed Nov 30, 2022 3:06 pm

Hi folks,

I'm hoping someone will be able to help me solve a problem with my 3.0Si E86.

A few months ago I had the error code of P0140 (o2 sensor, bank 1 sensor 2 - Circuit No Activity Detected). I had my local garage have a look and they said that they tested both downstream sensors and both were needing replaced so I agreed to them doing the work. A couple of days afterwards the check engine light came on again, this time with code P0140 and P0036 (heated oxygen sensor heater control circuit bank 1 sensor 2).

The garage had a look around and suspected a wiring fault, but were never able to find anything so I took it to another garage, an independent BMW specialist, who suggested that it was likely to be a fault with the Power Distribution Module as one of the fault codes on his diagnostics machine mentioned an o2 sensor heater circuit activation fault, so the signal was not being sent to switch the circuit on.

This morning I replaced the Power Distribution Module and sadly, the check engine light is still on, I did erase it with my OBD but it was back on within a couple of minutes.

Does anyone have any suggestions for where I should be looking next?

Thanks in advance

** UPDATE**

I took it back to the garage that had replaced the two sensors initially and insisted that they check the sensors before starting to pull the car apart to look for a wiring fault, as they had suggested. Thankfully they found that one of the two new sensors was faulty and fitted a new one under warranty. Thanks for the replies, without those I wouldn't have insisted on checking the sensors.

Smartbear · Post by **Smartbear** » Wed Nov 30, 2022 5:25 pm

I had similar with our Skoda yeti, changed the lambda sensor but the fault code wouldn’t clear - after driving myself mad looking for a wiring fault i found out the issue was caused by a faulty brand new Bosch sensor!
Rob

iain_Z4C · Post by **iain_Z4C** » Wed Nov 30, 2022 6:13 pm

Smartbear wrote: ↑Wed Nov 30, 2022 5:25 pm I had similar with our Skoda yeti, changed the lambda sensor but the fault code wouldn’t clear - after driving myself mad looking for a wiring fault i found out the issue was caused by a faulty brand new Bosch sensor!
Rob

Thanks, that sounds like it'll be worth investigating.

BumpyZ4 · Post by **BumpyZ4** » Wed Nov 30, 2022 10:23 pm

Happened to me too. Installed 4 new sensors and 2 months later the heating circuit failed on one of them.

iain_Z4C · Post by **iain_Z4C** » Tue Dec 27, 2022 1:58 pm

I've amended my original post with an update

Smartbear · Post by **Smartbear** » Tue Dec 27, 2022 6:07 pm

iain_Z4C wrote: ↑Tue Dec 27, 2022 1:58 pm I've amended my original post with an update

All’s well that ends well

Rob

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