Hi there guys and gals!

I have my son's S40 2004 with 140k with O2 sensor problems.

Diagnostic tool says

P0031 : HO2S Heater control circuit Low bank 1 sensor 1
p0037 : H02S Heater Control Circuit Low Bank 1 sensor 2

I replaced sensors cleared ECU and it came back again in less than 20 minutes driving..

I've checked the Harness connector I am getting 3 volts instead of 12 v but Am unsure this is the correct value on VOLVO .. I am a do it myself person.

I Checked the fuse box and none is tagged with O2 sensor feed label or such ...

is the 3v value correct ? , or what's the correct value?

Any help greatly appreciated..

 

Check fuse F33 under the hood...

 

Hi,
thanks for your reply, is that one called something around light bulb fuse?

its was blown and I replace and blow it again, I have the car with mechanic doing water pump replacement.. so i am unsure if same fuse that your showing here..

so it should be more that 3 volts.. then..
i knew it could be a fuse.., when i get the car back I will come back here..
Thanks.. for ur help.

 

Hi,

The fuse keeps getting nailed, I check harness cables for any short disconnected O2 sensors to see if they are not the culprit but nothing, I was reading somewhere that it could be vacuum pump circuit for brake servo ?

@habbyguy you have more information , i really appreciate your help.

 

volvowiringdiagrams.com may help - check out what is on that fuses wiring path...

 

thanks mt6127,

But that website volvowiringdiagrams.com is on error..

 

vacuum pump circuit for brake servo
was shorted, now old and new sensors are working fine.

thanks for kind support.