audi2l20v

Hi guys, I have a similar problem on my 2003 A8 with BFM engine. Recently it would start once a week if I'm lucky. A friend of mine checked it with VAG COM and VAS PC and it registered engine speed sensor fault (G28). Could you help me locate it - I would like to try cleaning it before replacing it. Thanks and have a joyfull quattro (drifting in a snow) time!

audi2l20v

that's the car





is this the engine speed sensor - located over the front left semi axle<br/>





some inspiration

MP4.2+6.0

Mister Bally has been through this as I recall and advised others. I remember the description as the crankshaft sensor if it is the same.

In general, I would not clean these. Just plug and play replace. They are typically Hall sensors and either work reliably or don't independent of cleaning. This one lets you down cold if it doesn't work, as you are finding. Major drag if not at home or shop. At least the cam ones let you keep going--with a CEL and lower state of tune. If its a Bosch part like the cam ones in my W12 as an example, you can get them under the Bosch # for well under half the dealer price for the identical part.

mishar

Welcome to the board!

Did you check the sticky tread?

audi2l20v

Thank you MP and Mishar! It is definately better to change the sensor with new one - it is a Bosh part, so I will look for it. From Mister Bally's experience, I understand that the sensor is located under the heat sheeld of internal CV joint, so it should be the one on my photo. Will try to dismount it soon. Thanks again, Emil.

audi2l20v

Just wonder what this opening is for? It's on the front bottom end of the gearbox

Petahs

I just did this on an 06 A8, had to remove both covers on the bottom as well as the heat shield on the drivers side you will have fun putting it back on! Have 3 or 4 zip ties so you can tidy everything back up.

Mister Bally

No idea what the hole in the bottom of the bellhousing is for. Perhaps a factory test sensor hole.

If you remove the sensor and there are iron filings between the magnet and the edge, wipe them away, reinstall and attempt to restart.

That said, based on several posters here, the sensor has reached the end of its useful life. I also say replace it since you are removing it anyway.

audi2l20v

Hello again, I have received new engine speed sensor and replaced it last week, the car starts again, but sometimes it takes a little bit more cranking to start - 5, 6 seconds instead of usual 2, 3 and it happens when the car is cold. During the replacement of the sensor there was an unpleasand surprise - torn boot of internal cv joint - so the fun of doing the job was also lubricated with some grease. I have the axle removed, replaced the boot, then assemble first the sensor and the heet shield and insert the axle last. So assembling was much easier than the disassembling. On YouTube there were some very usefull videos how to remove the axle without having to disconect the upper arms of the suspention - simply turn the stearing weel to the right and there is enough space for the axle to go out. So thanks again for the support!

MP4.2+6.0

Good to hear you are getting back on the road. Blown CV boot, especially on inside, is rare. It could be that the grease got on the sensor too.

On cranking, simply try some quality fuel additive that cleans fuel system and valves. If you were in North America, Techron is the norm. What ever is similar in Central Europe. If your car has enough wear to have things like a worn CV boot, I would change the fuel filter too. Good maintenance anyway, and may help with pump(s) longevity as well as fuel flow at the margin.