Urs4 aan not starting

[roysterFR]

I have a problem with my aan engined s4 where it is showing a g40 camshaft short to ground fault. I have tried new camshaft sensor, taking wire from plug to correct pin on ecu, checked all plugs etc. I then swapped ecus and it started briefly then cut out and again the same fault came back. I then tried my last spare ecu and the exact same. Could there be something causing ecu to short out? I have changed the fuel pump relay etc still the same fault, starting to tear my hair out with this. does anyone have any other ideas? Thanks

[Tractor Dave]

I'm not an expert (I'm sure one will be along soon) but have you recently replaced your alternator? There was someone here recently who fried his ecu after fitting a new alternator. The regulator was faulty and it allowed excessive voltage.

[roysterFR]

To be fair I hadn’t thought of alternator thank you, but I don’t think it gets going long enough to create any real voltage unless it’s possible just with turning over

[Vorsprung durch Technik]

How about the Immobiliser? Or maybe the older Urs4 doesn't have one?

[roysterFR]

Yes s4 has no immobiliser, I can’t understand why it started then cut out then refuses to start at all and shows always the g40 fault.

[Tractor Dave]

Have you done any work on the car before this happened? I think G40 is the hall sender which would indicate the timing is out. Have you got any spark? It could be that your ecu takes a few seconds to detect the code and then shuts the engine down. Removing the ecu however should clear the code. Have you tried putting one back in?
When mine would not start it took ages to diagnose. In the end I discovered the camshaft pulley key had sheared and the timing slipped slightly. I was very lucky there was no damage.

[roysterFR]

Hi yes timing belt etc all new and all marks ok and pulley ok, with original ecu it started then cut out then showed fault then nothing and then the same with my spare ecu which were both good and both showing the 00515 fault, I have changed the hall sensor twice both showing ok, and still the same fault. I have also ran wires direct to the correct ecu pins and still same fault. Very strange

[Tractor Dave]

Did you remove the top pulley (camshaft). It's very easy to damage the cut away that sends the signal to the hall sender.

[roysterFR]

Hi no sorry it’s one of the very first aan engines with the hall sensor where the dizzy would be

[Tractor Dave]

Ah. I'm suddenly out of my depth then. There is a good guide on non starting engines here. Search under the Forums and scroll down to engine and the first listed are sticky's. There will be a few to read there.

like this one

https://www.s2forum.com/forum/technical/engine-and-turbo/51040-1-definitive-engine-does-not-start

[roysterFR]

Yes have looked through what I can unfortunately it’s something well out of the ordinary area I think. I did wonder if a relay could hold in and become a problem or such like but have now tried or changed just about everything and still nothing, I don’t know if anyone knows if the holding relay in ecu could become a problem or short out.?

[Tractor Dave]

If it just started doing this after you changed the timing belt I would re check your timing marks and make sure you used the correct belt.

[roysterFR]

Will do but am sure they are fine, I am going to try the non working ecu in my other s4 and see if it runs if not I don’t understand what’s causing their failure and the g40 fault.

[Tractor Dave]

Good plan. Have a beer and do it tomorrow . Always works for me

[newsh]

Have you double checked timing from the marks on the flywheel?