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Discussion Starter #1 (Edited)
Hi,
Can anybody tell me if oil leaking onto the 02 sensor connector block could cause a short-circuit? I was under the impression the connection was water-proof?

I was expecting to find the connectors near the top of the engine, but there's nothing there, they are near the oil sump
 

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Discussion Starter #2
quick update
A guy from pelican parts says it's unlikely the oil will cause issues...my local mechanic agrees, my car had been misfiring before the 02 sensor code appeared, and he thinks its more likely that the misfires have affected the sensors.
The car's due a service anyway, so gonna start with new spark-plugs, see if anything changes.
 

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Discussion Starter #3
update:
new plugs haven't made any difference...I ordered a new 02 sensor which should arrive today, but the weather is pretty bad so not gonna get a chance to swap it out for a few days.
The misfires seem to be getting worse, so hopefully this will fix it
 

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Discussion Starter #4
So I changed the precat 02 sensor on friday, and the car ran beautifully...until sunday :(

diagnostic codes are the same as before the sensor change
P1204 (not sure what this is)
P1205 (not sure what this is)
P0130 (O2 sensor circuit B1S1)
P0150 (O2 sensor circuit B2S1)
P1341 (Multiple Cylinder Misfire With Fuel Cut-off)
P1343 Misfire Cylinder 1 With Fuel Cut-off
P1349 Misfire Cylinder 4 With Fuel Cut-off

Before I put the new sensor in, clearing the codes had no effect, and the codes would come back after one or two trips.
After I put the new sensor in, the car ran like new, and I drove a lot on Friday and Saturday...then on Sunday is started misfiring again.

My guess is that either the oil leaking onto the connection is causing a problem, or else the other section of wiring (not the section that I replaced with the sensor) might have a problem, and that just by messing with the sensor wiring I temporarily fixed it ???
 

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Discussion Starter #5
So I disconnected the sensor again, wiped all around and inside the connector block, and cleared the codes...car is running like new again ( for about 2 days anyway...we'll see if anything changes)
 

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Sounds like you're due for a valve cover gasket change. Buy a gasket and 15 (?) grommets. Make sure you buy OEM parts or you'll be redoing the job in 6 months. Also, buy a tube of high temperature RTV. There are YouTube DIYs for this.
 

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Discussion Starter #7
Hi Markus,
Thanks for the joining me...I was beginning to feel like a crazy person talking to myself in here :loco:

Can I ask, what makes you say that?
 

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The valve cover gasket tends to leak. It's just one if the "features" of the M5; engine. On the exhaust side of the engine the only place that can leak oil is the valve cover gasket.
 

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Discussion Starter #9
Hi Markus, sorry for not getting back to you. (the car has been running beautifully btw)

Now I understand why you said that...however the sensor connectors are not where you expect them to be, they are right down at the bottom of the car next to the oil sump.

The VCG is fine, the vacuum pump had a leak when I bought the car, that's fixed now. ( although there is still a leak somewhere...haven't looked for it properly yet )
 
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