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  #11  
Old 17th November 2018, 04:45 PM
erubus erubus is offline
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I swapped the sensor over today with a brand new OEM Bosch one - identical to the one that was in it. Surprisingly easy to do, took less tha ten minutes once I had found a suitable tool (which took 45 minutes).

Once it was swapped over and securely plugged in, I replaced the battery, freshly charged. Made sure all the codes were cleared tghen went for a start attempt. Engine just span over, still not starting.

Scanned it again and got the same fault... p3007 cam position sensor g40 no signal. Cleared again and tried another start. same code. Did that three or four times until the battery was struggling to turn the engine again. Every time its the same cam sensor no signal fault.

The plan now is to try and find out which pins on the ECU connector are for the three cam sensor wires and test for continuity in case a wire has broken in the loom somewhere.

I did output tests on everything I could think of that might affect starting and everything seemed to be moving fine, swirl flap actuators, turbo actuators, EGR etc etc.

The only other thing I can think of is to remove the sensor and stick an endoscope down the hole and see if the camshat is actually moving - I'd expect that there would be some sort of unusual noise coming from the engine if one of the cam chains had snapped though!!

Has anyone got any suggestions? Am i barking up the wrong tree with the cam sensor? None of the measuring blocks are labelled on VCDS with this car, or the last two A8's so Ive no idea what I should be looking for to see if there is any signals at all coming from the sensor.

Gill
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  #12  
Old 17th November 2018, 06:16 PM
Joe2.0E Joe2.0E is offline
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Is it possible that catastrophic fuel pump failure could have caused all your bother ?
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  #13  
Old 17th November 2018, 07:21 PM
erubus erubus is offline
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I dont think so. The fuel pump was one of the things I did an output test on and it certainly ran. Running through the output tests there was one for fuel pressure regulator and the pressure was up in the region of 300bar iirc.

Ive been searching to try and find some information on the ECU connector pins but cant find any info anywhere. I don't fancy having to cut all the loom up to follow the wires looking for a break that might not even be there.
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Daily drive: 2008 A8 4.2TDi
2003 A8 4.0TDi. 4 zone climate, double glazing, Bose - dead
Other cars: 1980 Land Rover Series 3, 2.25d, hydraulic winch,Van/station wagon/topless depending on my mood
1990 Land Rover 90 factory county station wagon with all the luxury additions, such as a clock and a tape player.
2007 A4 3.0TDi s-line cabriolet quattro
2000 A8 D2 2.8 quattro, looking for a new home - gone
2003 A6 3.0 quattro, in the way... anyone want any parts? - gone
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  #14  
Old 17th November 2018, 07:30 PM
MikkiJayne MikkiJayne is offline
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G40 wiring here:



Interesting that the V8 tdi only has one, compared to two on the V8 petrol engine. Without it, the ECU knows the engine is turning, but not what state it's in which would explain why it won't start.

Unfortunately I can't find any reference to the sensor or fault-finding it in Elsawin

This might also be useful if you're going to check the wiring:



I'm not sure if the reference to adaption values applies if you simply unplug the ecu and plug it back in later but worth noting anyway.
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  #15  
Old 17th November 2018, 08:13 PM
erubus erubus is offline
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The petrol might have two because it has variable camshafts (I think) so one for exhaust cam and one for inlet. I actually thought it had four but don't know where I got any of the above from.... Maybe I made it up!

Thanks for the diagram,. I'm not sure I understand which pins I need to look for though. Do I just look for 27 through to 29? It's the t60/b hats throwing me. I get the j623.

I read the bit at the bottom, actually read through the whole document but didn't twig there might be adaptations to do afterwards. Definitely something else to read up on to make sure I don't bollox it up!

Thanks again, gill
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Daily drive: 2008 A8 4.2TDi
2003 A8 4.0TDi. 4 zone climate, double glazing, Bose - dead
Other cars: 1980 Land Rover Series 3, 2.25d, hydraulic winch,Van/station wagon/topless depending on my mood
1990 Land Rover 90 factory county station wagon with all the luxury additions, such as a clock and a tape player.
2007 A4 3.0TDi s-line cabriolet quattro
2000 A8 D2 2.8 quattro, looking for a new home - gone
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  #16  
Old 17th November 2018, 08:26 PM
MikkiJayne MikkiJayne is offline
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The petrol engines have one on each inlet cam so the ecu has feedback from the variable chain tensioners which alter the inlet cam timing relative to the belt-driven exhaust cams. Presumably the TDI doesn't have variable cam timing so it doesn't need any more than one sensor.

There is a 60-pin connector and a 94-pin connector on the ECU so T60b is the smaller of the two. G40 is on pins 27 (5V, red/yellow), 28 (signal, white) & 29 (ground, brown). At the G40 sensor connector, with the ignition on, you should see 5V across pins 1 and 3. You'd need an oscilloscope to see the output from it when the engine is spinning.

If you get 5V at the connector then a continuity check back to the ecu on pin 2 to T60b/28 should prove out the wiring.

Last edited by MikkiJayne; 17th November 2018 at 08:29 PM.
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  #17  
Old 18th November 2018, 09:02 AM
erubus erubus is offline
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Brilliant, thanks. Unfortunately, I have to go down to York today for a week for work but I'll check this as soon as I get back.
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Daily drive: 2008 A8 4.2TDi
2003 A8 4.0TDi. 4 zone climate, double glazing, Bose - dead
Other cars: 1980 Land Rover Series 3, 2.25d, hydraulic winch,Van/station wagon/topless depending on my mood
1990 Land Rover 90 factory county station wagon with all the luxury additions, such as a clock and a tape player.
2007 A4 3.0TDi s-line cabriolet quattro
2000 A8 D2 2.8 quattro, looking for a new home - gone
2003 A6 3.0 quattro, in the way... anyone want any parts? - gone
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  #18  
Old 19th November 2018, 05:36 PM
erubus erubus is offline
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My dad was speaking to a customer today about this. This guy runs a specialist VAG garage. He apparently reckoned the cam sensor needed programmed in. Is this the case, and if so how is it done?

I'll need to try and find which measuring blocks do the fuel rail pressure and test them to make certain I'm getting fuel through.
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Daily drive: 2008 A8 4.2TDi
2003 A8 4.0TDi. 4 zone climate, double glazing, Bose - dead
Other cars: 1980 Land Rover Series 3, 2.25d, hydraulic winch,Van/station wagon/topless depending on my mood
1990 Land Rover 90 factory county station wagon with all the luxury additions, such as a clock and a tape player.
2007 A4 3.0TDi s-line cabriolet quattro
2000 A8 D2 2.8 quattro, looking for a new home - gone
2003 A6 3.0 quattro, in the way... anyone want any parts? - gone
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  #19  
Old 19th November 2018, 08:15 PM
MikkiJayne MikkiJayne is offline
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Hmm I'm not sure about that. Its a simple hall sensor which detects a slot in a spinning metal disc. There is nothing to program, and there's no intelligence in it. There's certainly nothing of the sort needed on the petrol engines which use the same sensor.

When you changed the sensor did you check to see if the disc was still secure on the end of the cam? Theoretically, if that came loose the ECU might report it as open circuit when it didn't get a signal from it when it expected one.
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  #20  
Old 20th November 2018, 07:26 AM
erubus erubus is offline
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That's what I thought to be honest. Unless it needed told what the baseline responses from the sensor at various speeds was but I can't see it, it would just be an analogue wave. I've changed the crank sensor on the old 4.0 and didn't need to do any programming.

I'll need to get an endoscope dug out to check if the excitor wheel is still there, I would guess it's pretty well attached but it's not inconceivable that the cam chain or something has broken.. I'd be very surprised. It's annoying not being at the car to check things!
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Daily drive: 2008 A8 4.2TDi
2003 A8 4.0TDi. 4 zone climate, double glazing, Bose - dead
Other cars: 1980 Land Rover Series 3, 2.25d, hydraulic winch,Van/station wagon/topless depending on my mood
1990 Land Rover 90 factory county station wagon with all the luxury additions, such as a clock and a tape player.
2007 A4 3.0TDi s-line cabriolet quattro
2000 A8 D2 2.8 quattro, looking for a new home - gone
2003 A6 3.0 quattro, in the way... anyone want any parts? - gone
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