What sensors are these?

[geneandbolly]

can anyone tell me what sensor is what? i took this shot from the nearside wing looking down at the back of the engine . .



i believe that one of them is the engine speed sensor - is that the same as "crank position sensor"/ "crankshaft pulse sensor" as seen here?

http://www.ebay.co.uk/itm/1812273972...%3AMEBIDX%3AIT

[Error404]

engine speed & crank reference

[geneandbolly]

hmm . . sorry for being a bit thick here, so which one is this and does it replace the one on the left or the right on the photo? vag com said that the "engine speed sensor" was faulty. i'm confused!!

http://www.ebay.co.uk/itm/1812273972...%3AMEBIDX%3AIT

[Error404]

The engine speed sensor is the rearmost one it references the teeth on the flywheel to give the ECU & instruments an RPM signal.
The crank reference is the forward one, it references the timing pin on the flywheel to give the ECU a crank position signal.
Both of them work exactly the same and AFAIK are interchangeable. From memory the grey plug is the engine speed sensor but I could be mistaken.

HTH
Alex

[geneandbolly]

thanks for your help with this. so, in effect, the sensors are identical but have two different functions ie could i buy two of the same sensor and replace both of them on my car? i take it that vag com is picking up a fault in the rear most sensor on my s6 then?

[rynaqui]

thanks for your help with this. so, in effect, the sensors are identical but have two different functions ie could i buy two of the same sensor and replace both of them on my car? i take it that vag com is picking up a fault in the rear most sensor on my s6 then?

G28 (Engine speed sensor) will always show up when the car is not running, if any of these sensors are not working I believe the car will not start

Not sure if they are interchangeable or not..

[Vorsprung durch Technik]

G28 (Engine speed sensor) will always show up when the car is not running, if any of these sensors are not working I believe the car will not start

Not sure if they are interchangeable or not..

I was thinking that.If either of those sensors are faulty car will not start at all.If you car is working fine why change?

[Error404]

As above, G28 fault is always present when engine is off.

[UrS4boy]

Crank Position (G4) and Engine Speed Sensor (G28) Info - Function , Location and PNs

Error404 nailed it but in case you want to read more, click on this link:

http://forums.quattroworld.com/s4s6/msgs/20986.phtml

And as mentioned, you will always get a G28 failure code *IF/WHEN* you pull the codes with the engine off. It's a false positive and not to worry, they rarely truly fail, if ever.

[Bowie69]

I changed both of mine because I used to get failed starts in hot weather after leaving for 10mins, really annoying when popping to the shops -I don't get them any more

[UrS4boy]

G4 Crank Position Sensor and G28 Engine Speed Sensor Maintenance

I changed both of mine because I used to get failed starts in hot weather after leaving for 10mins, really annoying when popping to the shops -I don't get them any more

That is interesting. I am having a hot restart issue with my RS2'd AAN in my 93 UrS4 that I can not figure out. I have no codes. I removed and cleaned my G4 and G28 sensors, including the ends at the flywheel and the connectors at the firewall. No change. Link to the post below.

Did you determine which of the sensors was the problem or did you just replace both?

http://forums.quattroworld.com/s4s6/msgs/281029.phtml

[Bowie69]

I just replaced them both, I was always in a hurry to get the car running again, and the only thing that seemed to work was opening the bonnet and let it cool off.

As it was (and is now) a daily driver I wanted it 100% reliable, and so far, apart from a dicky supposedly refurbed fuel injector, it has been

If you do change them, they are likely corroded very badly into the alloy holding block, took a hacksaw, drifts and a lot of patience to get them out once in a vice. Careful how you clamp it too, you can crack the alloy if you squeeze it a little too much

[UrS4boy]

...If you do change them, they are likely corroded very badly into the alloy holding block, took a hacksaw, drifts and a lot of patience to get them out once in a vice. Careful how you clamp it too, you can crack the alloy if you squeeze it a little too much

Thanks.

If you read my link above, I had no problems removing my G4 and G28s from the engine to do a clean and maintenance on them.

I can always get my car to hot start if I crack the throttle open a tad (i.e. take it off the idle switch) so my issue might not be G4/G28 related.

[Bowie69]

Yeah, doesn;t sound like it, mine was dead to anything, I think it was no spark related, but it was many years ago it was happening, but when I recommissioned it earlier this year after reading on here it seemed a good thing to do

[geneandbolly]

thanks for the input, chaps. i was getting a fault code regarding the engine speed sensor, but like you say, i think it was when the car was switched off. there are no issues with poor starting.

cheers!