Low voltage to cam sensor 2008 2.0 tdi

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Hi guys.

This is my first post here,  mostly because this is my first Audi problem that I have not been able to cure for probably 20 years.

I did search for this problem but I couldn't see any that refers to  "cam sensor low voltage",  if this has been covered then please guide me to the link.

The car is a 2008 A4 2.0 tdi S line. 85,000 miles.

The car is difficult to start (almost impossible) unless it is hot then it'll start right away as it should.

We did a diagnostic and it shows low voltage to cam sensor,  I checked the plug going to the cam sensor lead,  this is marked (1) (2) (3).

From reading I found the number 1 pin should be 12volts reduced to 5 - 7 volts when running.

Number 2 pin is the sensor wire,  again this should be 12 volts and between 5 - 7 volts when running.

Number 3 pin is Earth.

Firstly I would like to know if this is correct as it is kinda important to know.

I have between 2 and 3 volts to wires 1 and 2.

This is my question.

Where do these wires connect to ? if it is the main ECU then it is probably that the ECU is faulty ?

Is this a normal / common issue with these cars or is it rare ? if it is common then please tell me the cure.

I have a ECU guy that can check and repair,  but he is a bit spiteful,  so I dont want to just give him the ECU unless it is likely that the ECU is faulty.

Please help if you can as the car is now off the road.

Many thanks.

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Really,  no one ?

Can anyone recommend an Audi specialist in the Cambs area ? or even someone who I could talk to to ask if the problem is in the ECU ?

Is this thread even live, can anyone see it ?

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Hello Steve,

Not that I have any responsibility for the good running of this forum ( for which I have the utmost respect) but I feel I have to ‘justify’ its potential as a source of help. I do appreciate however, that advice maybe slower in coming through - if in fact it does at all, and in your case where I anticipate your appeal for help was probably posted around midnight, I would realistically doubt anyone would have replied by now. Of course from your point of view, time is probably important since the car is immobile, but ...’ .....Really, no one?’ may not have been seen as the most appropriate comment to have made . Sorry Steve, and this is just my personal opinion, and probably is not shared by others. 

Anyway, onwards and upwards, and unfortunately my response is not going to help you very much, but I think that if this were mine, I would be seeking local specialist adivce with this one, if no one comes up with a simple fix explanation for you in a short space of time. 

Good luck in getting it sorted.

Kind regards,


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As my post was posted 23 hours ago and it is now 6:45 pm -ish,  it means my post was posted about 6:30 -ish last night and not at midnight.

Either way,  a full day later and not one word of advice,  but I was told off so at least I know this thread is live.

"Really,  no one" was posted 8 hours ago being 10-ish this morning.

I do not know how this forum works but I remember my very first post on a car forum asking for help and almost immediately I was chatting to half a dozen guys who 17 years later I am still friends with,  I guess forums have changed,  or is it the willingness to help others ? -  rhetorical .


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Hello Steve,

Thanks for the explanation. I think this forum works like most others run on a volunteer assistance basis, and I seriously doubt whether anyone on here would be reluctant to help you out if they can. Experts are few and far between and its likely that their expertise has been built up by hands-on experience of a particular marque, perhaps being full time employed in such roles, and may indeed just not be bothered to have their free time interrupted. I think it’s fair to say that the majority of contributors on here are enthusiastic, and really want to help - if they can. If they cannot, then I am sure it’s not from a lack of interest or desire trying to help. 

I think it’s great that you found friends on a forum all those years back, and no doubt in-depth electronic issues were in their infancy then, and plain hands-on experience in things mechanical could be more readily shared. 

Let’s hope someone on here will be able to help you out Steve, or forum members nearer your neck of the woods be able to recommend some local specialist assistance.

Please don’t look on us to harshly Steve, and if it’s any consolation, it’s quite possible that the good folks who administer this forum will not look on my responses too favourably, but it’s a risk everyone takes if they respond to posts. 

I genuinely wish you good luck in getting it sorted. 

Kind regards,


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