# need help with finding o2 sensor fuse



## venom_vdub (Jul 6, 2009)

im throwing codes for o2 sensor and am throwing the same codes after i cleared it and replaced sensor im getting these 3:sly:

p0031
P0037
p0135


this is leading me to believe that i have a blown fuse or a short because, i replaced the sensor, cleared the code and they come back .. plus my car running like ****, my a/f is off, inlcuding me running pretty f*****g lean
does anyone know where this fuse or circuit is? google wont tell me lol i cant find a diagram:banghead::banghead:


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## groggory (Apr 21, 2003)

I don't know where the fuse is, but here's my notes on the front o2 sensor

For AWP engine code

Front o2 sensor

o2 harness plug
Pin 3 is heater +
Pin 4 is heater gnd

Heater + is 12v with ignition keyed on

Ecu pin .. Harness Wire color .. o2 connector number ... o2 sensor wire color

52 .. grey/red .. 6 ... Red
71 .. black .. 2 .. Not connected
51 .. grey/white .. 5 .. Yellow
70 .. green .. 1 .. Black
5 .. white .. 4 .. White

Relay 87A .. blue/red .. 3 .. Grey

...

So if you unplug your front o2 sensor and key the engine on, you should get +12 between pin 4 and pin 3


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## AmIdYfReAk (Nov 8, 2006)

heater is Fuse 43, but it powers WAY more than just the O/2.


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## Weehe (Apr 2, 2010)

Don't want to sound stupid, but if you replaced the sensor and it is still throwing the code pretty sure that means you have a leak somewhere making it lean (which throws the code).


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## quiksilver18T (Jul 29, 2002)

groggory said:


> I
> Ecu pin .. Harness Wire color .. o2 connector number ... o2 sensor wire color
> 
> 52 .. grey/red .. 6 ... Red
> ...


 Groggory, 

I've got a p0030 and a p0135. With the old and my new O2 sensor... Wondering, do u know where the Relay 87A pin is? I've searched the FAQ and found relay locations, can't figure where this is.... 

That said, 87A on some Bosch relays looks to be an "on when switch off"


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## groggory (Apr 21, 2003)

I have a suspicion the o2 heater is switched by the fuel pump relay


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## speed51133! (Aug 5, 2002)

Get a vag com scan. And yes. Fuel pump relay.


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## quiksilver18T (Jul 29, 2002)

Thanks for the reply. 

I just removed the lower portion of the driver's side dash and got to the Fuel Pump relay (position 4 on lower). No luck... can't find a wire that matches the blue/red color of the O2 heater wire.... 

argh.... 

I need to get a hold of a real Bentley. I have an electronic copy that I found floating on the net, but it doesn't have wiring schematics.... 

P


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## Mindfault (Feb 2, 2010)

Fuse 43 is where she ends


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## AmIdYfReAk (Nov 8, 2006)

AmIdYfReAk said:


> heater is Fuse 43, but it powers WAY more than just the O/2.


 


Mindfault said:


> Fuse 43 is where she ends


 :laugh:


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## Mindfault (Feb 2, 2010)

I have a schematic of the circuit posted somewhere on here, groggory and i have had discussions about this before. 87a is just a leg of a relay, and that schematic will show you where it is. Also, if i remember correctly, i couldnt find it, and i just replaced fuse 43 and viola:wave: also, 87a may be a wiring circuit number, it isnt necessarily a relay. There are alot of things in that circuit. Evap and such. So. Find that diagram yo


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## Mindfault (Feb 2, 2010)

http://forums.vwvortex.com/showthre...h-my-unitronic-tune.-chime-in-unitronic/page2 

There you go. 87a isnt a relay its just a connection


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