# Crank Sensor Fault?



## chur1996 (Feb 24, 2010)

Scary experience driving home from work tonight: in the middle lane of the motorway doing about 70 when all of a sudden the revs died to zero, surged again to what they were and then died again. Engine cut out although the electrics stayed on, manage to coast to the side of the motorway and then luckily down a motorway exit slip road.

Let it stand for a minute or so before trying to re-start it, turned over but never caught. Problem. Feared it might be a big problem of the timing belt going and taking the engine with it. Sat there with the bonnet up for about an hour until recovery turned up, embarrassingly it fired up when he got there!

He plugged his diagnostic computer in, and it threw up a crank sensor fault (along with another, possibly engine speed sensor but can't remember). He seemed to think this would be the cause, cutting the engine out when it heated up. Managed to get it home, and will take it in to a garage tomorrow morning.

Does this sound like the probable cause? And do they usually need a new sensr or just a good clean/check of the old one?

At the moment i'm just happy that I'm not looking at an engine rebuild to be honest!


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## fozzie34 (Jan 18, 2011)

As you had it scanned, it certainly makes sense that the crankshaft sensor is the most probable culprit. I can feel your relief that the engine hasn't detonated


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## Lovinit (Mar 5, 2011)

i've had this happen to me...although not so drastically.. glad your safe mate..

i drove to wrok one morn all was fine...but when i went home car wouldnt start...trurn over but wouldnt fire.... had it checked on VAGcom... and said something about speed/cam sensor.. seemed a wire had worked its way loose...or something like this..

Mechanic fixed it and since then no probs..

hopefully it is as simple for you.

James


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## Lovinit (Mar 5, 2011)

i've had this happen to me...although not so drastically.. glad your safe mate..

i drove to work one morn all was fine...but when i went home car wouldnt start...trurn over but wouldnt fire.... had it checked on VAGcom... and said something about speed/cam sensor.. seemed a wire had worked its way loose...or something like this..

Mechanic fixed it and since then no probs..

hopefully it is as simple for you.

James


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## chur1996 (Feb 24, 2010)

Cheers guys, it was a bit worrying but luckily the motorway was fairly quiet!

Will it have done any damage anywhere, or will it just be the sensor that needs sorting?


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## fozzie34 (Jan 18, 2011)

chur1996 said:


> Cheers guys, it was a bit worrying but luckily the motorway was fairly quiet!
> 
> Will it have done any damage anywhere, or will it just be the sensor that needs sorting?


Hopefully you will get away with just a new sensor


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## John-H (Jul 13, 2005)

Speed sensor and crank sensor are the same thing. See the FAQ for details on changing it.


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## chur1996 (Feb 24, 2010)

Looks like it was just the sensor, garage rang this morning to say they've changed it and it seems fine after a test drive.

Just need to take it for a run on the motorway to be sure. Lucky escape I think!


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## chur1996 (Feb 24, 2010)

Sorry to revive this thread, I had a new crank sensor fitted as per the above and the car has been running fine.....until New Year's Day when I was driving from my Mum's house to my girlfriend's house (about 70 miles, over the Woodhead Pass) when it decided to cut out again!

Luckily not on the Pass itself, but on an A road about 5 miles from my Mum's. Pulled to the roadside, turned it off and then on after about 30 seconds when it luckily fired up again.

Made it over the pass (didn't fancy doubling the distance by going across the M62 and down the M1) although at times the revs were fluctuating slightly. Engine management light came on when I re-started it, although this disappeared yesterday when I started it.

Drove to work and back today, at certain points I could feel the engine hesitate for a fraction of a second but not cut out. Bit puzzled as to why this should be happening so soon after having a new sensor fitted, has anyone else suffered similar problems? Could it be a different sensor causing this fault? Obviously there is always the possibility that the garage has done a poor job of fitting it I suppose!


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## John-H (Jul 13, 2005)

Cutting out is usually when the ECU can't detect the crank position (which has been fixed). Sometimes an over boost situation (occurs because someone has fitted an N49J solenoid which doesn't suit the map and sometimes a faulty throttle sensor is diddly ignored by the ECU (rare). The latter would still allow the engine to idle but there would be no throttle response, the over boost would stop any turbo action but the engine would still work normally aspirated. The crank sensor stops the engine.

Another issue could be coil packs being intermittent and causing hesitations and drop our revs momentarily.

Get you fault codes read again to help diagnose this further.


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## yoshimi (Feb 7, 2012)

I am having this same problem with my 2000 Audi TT!
I was driving yesterday, and the brake light came on and the ABS light, and my car started beeping at me. 
I kept driving, and turned it off for an hour when I got to my destination. When I got back in my car, the engine wouldn't start. It sounded like it was going to, the first part of starting my car went normal, but the engine just didn't start after turning the key and hearing the normal starting sound. 
I thought it was the battery at first, and bought a new one, and installed it, and it worked. Then today it wouldn't start again! I took it to Auto Zone, and they plugged it all up and said that the engine either has a poor electrical connection, faulty CKP sensor, and possible low fuel pressure or a vacuum leak on the engine, or Failed HO2S (Heated oxygen sensor). 
I'm going to take it to Audi later today. Hope it won't cost too much!


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