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  • Urs4 aan not starting

    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

  • #2
    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.
    Nothelle S2 Avant
    Black Ur project
    Ocianic Ur project gone
    S2 Coupe project gone
    Urs6 plus project gone

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    • #3
      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

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      • #4
        How about the Immobiliser? Or maybe the older Urs4 doesn't have one?
        96 URS6 plus speck saloon
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        94 2.6 80 Avant
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        • #5
          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.

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          • #6
            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.
            Nothelle S2 Avant
            Black Ur project
            Ocianic Ur project gone
            S2 Coupe project gone
            Urs6 plus project gone

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            • #7
              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

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              • #8
                Did you remove the top pulley (camshaft). It's very easy to damage the cut away that sends the signal to the hall sender.
                Nothelle S2 Avant
                Black Ur project
                Ocianic Ur project gone
                S2 Coupe project gone
                Urs6 plus project gone

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                • #9
                  Hi no sorry it’s one of the very first aan engines with the hall sensor where the dizzy would be

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                  • #10
                    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/techni...does-not-start
                    Nothelle S2 Avant
                    Black Ur project
                    Ocianic Ur project gone
                    S2 Coupe project gone
                    Urs6 plus project gone

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                    • #11
                      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.?

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                      • #12
                        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.
                        Nothelle S2 Avant
                        Black Ur project
                        Ocianic Ur project gone
                        S2 Coupe project gone
                        Urs6 plus project gone

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                        • #13
                          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.

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                          • #14
                            Good plan. Have a beer and do it tomorrow . Always works for me
                            Nothelle S2 Avant
                            Black Ur project
                            Ocianic Ur project gone
                            S2 Coupe project gone
                            Urs6 plus project gone

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                            • #15
                              Have you double checked timing from the marks on the flywheel?

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