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Discussion Starter #1
OK my engine is an AUF Auto 2.5 TDI 102BHP

The car has had a couple of intermittent starts recently where it started fine and then i went for a short drive and then when i tried to restart the car it would turn over but not start. eventually i would leave it 5 minutes or so and it would then start fine.

I thought it might just be a bit of a dodgy 109 relay.

So yesterday it finally died properly!!

Car was fine and then after checking the fuel pump timing it doesnt want to know anymore.

No glow plug relay and no start, also unable to talk to the Engine control module via VCDS. immob and clocks are ok. when we try to get into the ecu it says "too many errors to continue"

so checked all the wiring for the 109 relay and the black and white wire seems to be ok, good continuity from fuse block to ecu.

thought it could be a CAN bus fault but again all the wires buzz out ok so not a wiring fault on that side.

To me it seems like the ECU is not getting power from relay 109 but all the checks have shown that the relay is ok (even got a new one just in case)

Mainly thinking it is a wiring fault on the canbus side of things or the relay 109 circuit.

Anybody got any ideas on where to go from here?
 

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Discussion Starter #2
i will add that the car did start after the fuel pump timing check so nothing to do with that. it has also recently had a recon auto gearbox fitted.
 

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Discussion Starter #3
could a bad earth cause these issues?

Or isit the immobiliser doing its job and immboilising?

What does the immobiliser do to do its job? as in what would be the symptoms if it was working correctly and doing its immobilising?
 

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Sounds like air in the fuel line as a possibility, so is the fuel getting through if not where is it stopping.
 

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Had a similar problem with my girlfriends polo, it wouldn't communicate with the ecu at all, turned out to be a dodgy relay for the ecu supply. Usually with an immobiliser kicking in it will start but die within a second.
 

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Discussion Starter #9
yeah i am not even getting a glow plug light or communication with the ecu, i am guessing it is a wiring fault or eco or the immobiliser has kicked in and stuck on.
 

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Mine sometimes does exactly the same.

Turn key, normal lights on dash, but no Coil light (this is on a cold engine). Engine will turn over but never start. I think its related to the management Imobiliser. When it plays up I have a bypass to get the engine going.

Just to clarify, send power to the selenoid and it clicks out of possition so that works ok, pump all ok, etc etc.

I think its a break in the wiring loom or a bad earth, I need to spend some time on it to fix as its doing it more often.

I can PM you the details how I bypass the system, I dont want to publish on public facing forum.
 

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Discussion Starter #12
so i am back to thinking about this.

what would stop me being able to read the ecu with vcds?

I connect up and can see immob instruments etc etc but i get no communication from the engine controller.

Is this because the ecu is not being powered because of a fault with 109?

black and orange CAN bus wires buzzed out ok from fuse box to ecu.

black and white wire buzzed out with a resistance of 1 ohm
 

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Discussion Starter #13
Also i can read the Auto trans ECU but it comes up with loads of faults, i am guessing this is because it goes via the engine ecu and as this cannot be read it sees all replies from the auto ecu as faults OR is it another symptom?

please someone help me out i am going mad thinking about this plus i go away in a week for 6 months and the wife needs the car!!
 
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