Daniel917

what can cause the yellow oil sensor light to pop up and stay on ? some tell me water temp sensor others oil level sensor.. im thinking of changing the oil temperature sensor since " my oil temperature gauge is not showing nothing so im guessing thats the problem .. if anybody has an idea please let me know thank you

Just Me

Oil temp gauge on cold. Oil temp (??? gotta accept your claim) light on. And you are asking if the two might be connected? What's th quetion?

Daniel917

oil sensor light on .. and my oil gauge states is on cold all the time the neddle never moves >> question is if its the oil temperature sensor >>

mithrilG60

Oil temp and oil level are on a single sensor located in the oil pan on all C5 A6's. A third function, oil quality, was added to that sensor for the 4.2, S6 and RS6. The yellow oil warning light in the dash indicates low oil level, but it could also be indicating a failed sensor if the dash is not getting any reading from the sensor.

Make sure you buy the OEM Hella part, and not the cheapo Merle. The Hella may cost double, but the Merle's are notorious for not working properly so you're just going to be replacing it again.

jcman

The SRI (Oil Level Thermo Sensor) that fits all C5's (Including 4.2,S6 and RS6) only has two functions; Yellow oil level symbol and oil temp gauge with three wires according to the eBahn/Bentley wiring diagrams, then there is the separate pressure "switch" to activate the Red symbol. Nowhere do I see a oil quality function? Please enlighten me because the service interval
channel 45 don't count, it's just an service event timer.

MP4.2+6.0

I have a 2000 4.2 and have seen the sensor many a time when doing oil changes. Similar looking sensor on my 2006 A8 W12. I know the latter is enabled in Europe to allow extended change interval--up to 2 years, 19K miles IIRC, and (much) shorter if conditions are severe on the other hand. Part of the German/Euro green movement on the one hand, and on the other hand turned off in the U.S. on newer Audis against the perception Americans don't accept/trust overly long change intervals. Owning a Mini, people grouse constantly about the long indicated change intervals there--14K or more indicated miles to service on high strung turbo's not uncommon for example.

It's not just a sensor AFAIK, but algorithms looking at other relevant parameters like speed, number of starts, operating temps, etc. I have seen the enabling configuration w/VAG COM on the A8 before (still under Audi's old (discontinued) seven year extended service deal so I have left it be so far), but I haven't bothered to look at the VAG COM options on the C5 A6.

mithrilG60

Read your manual, the V8 cars also use that sensor to read the amount of carbon build up in the oil and uses that to speed up or slow down the rate the service interval counts down. This is an oil quality reading and is it not a feature found on the V6 powered vehicles. It's actually a V8 specific sensor, it's also used on all later model V8 VAG products up to at least the FSI engine, I believe the sensor was redesigned starting with that engine but I could be mistaken there.

jcman

I believe that you are mistaking the functions of this component vs. software i.e. computer, this sensor has only two parameters of function as an input to the dash module.

Now I'm aware of the Hella PULS (packaged ultrasonic level sensor)

"Hella's second generation oil-level sensor has been standard equipment on a number of European vehicles since 2006. The first generation of oil level sensors was introduced in 1994. Hella's premium version of the oil sensor, called PULS+C (packaged ultrasonic level sensor + condition), also monitors oil quality."

This is quoted straight from a Hella source and not equipped in North America Audi's until after 2006 only on selected models and not on any C5 models, not even the RS6.

mithrilG60

No, I'm not mistaking anything. In the V8 cars this sensor reads oil quality, and that reading is used by the ECM to calculate the value to display in the service indicator.

C5 Bentley Service Manual, pg 17-6:
*emphasis is my own

The independent functions of oil level sensor and service interval counter you're describing is only applicable to the V6 cars. In the V8 cars the service indicator is not a simple dumb counter like in the V6's, in the V8's the oil level sensor works with the service indicator software in the computer to provide a more accurate calculations of the actual time before service is required.

For various reasons I have reset that service indicator to it's default of 12,000km several times in my car between oil changes, in each case the reading was back within 50km of the previous reading after only a few kms of driving. The only possible explanation for that behaviour is that the computer can in fact also monitor oil quality in addition to temperature and level.

Perhaps the sensor is the same and the V8 ECM is simply able to read additional input off it which the V6 cars can't? Who knows, all I know is that the oil level sensor does in fact provide a third additional function for V8 powered C5 A6'S

MP4.2+6.0

Here is the text from the Audi SSP on the 5V 4.2 dated Sept 1999:

Oil Level Sensor

The oil level sensor functions as an
information sender which allows the
flexible service interval to be calculated and
the oil level warning to be displayed in the
instrument cluster.

The Flexible Service Interval
feature will be available on U.S.
models at a later date.

The second paragraph presumably refers to the feature not being enabled, as opposed to the sensor not being there at all.