Tomandrew10 Posted June 19, 2025 Report Share Posted June 19, 2025 Hi, I’ve got an issue with my Gti it cranks over and tries to start but cuts out sometimes it just keeps cranking but doesn’t fire. The fuel pump seems to pressurise sometimes when the ignition is put on but other times it doesn’t. Checked spark and all ok. Battery voltage is 11.7. Checked fuse for fuel pump and that’s ok. The car has been stood for a week or so. Does anyone know what might be causing this? Thanks 1 Quote Link to comment Share on other sites More sharing options...
sj2112 Posted June 19, 2025 Report Share Posted June 19, 2025 Have you tried putting a jump pack/trickle charger on the battery? 2 Quote Link to comment Share on other sites More sharing options...
lupogtiboy Posted June 20, 2025 Report Share Posted June 20, 2025 Have you put a scanner on it? My bet would be the crankshaft sensor, utter b@stard to change 1 Quote Link to comment Share on other sites More sharing options...
mk2 Posted June 20, 2025 Report Share Posted June 20, 2025 Can you smell any fuel at the exhaust? If not, could be fuel system related, like pump, filter, pressure regulator, that sort of thing. Not ECU. Not temp sensor. Not ignition or plugs. And like @lupogtiboy says, crank sensor? You'll get no or intermittant sparks if it's the crank sensor. 1 Quote Link to comment Share on other sites More sharing options...
Tomandrew10 Posted June 20, 2025 Author Report Share Posted June 20, 2025 Had a carly code reader on it and didnt get much back, so borrowed a Vagcom lead and read the codes on that. Come up with low voltage to ECU is preventing start. Going to charge the battery up and have another go over the weekend. Didnt think it would be battery related as it turned over no problem! Yeah spark seemed fine so hoping the cranks sensor is ok. Thanks for the replies! Quote Link to comment Share on other sites More sharing options...
mk2 Posted June 20, 2025 Report Share Posted June 20, 2025 You won't get a code for crank sensor... Fuel problem then? Quote Link to comment Share on other sites More sharing options...
Tomandrew10 Posted June 22, 2025 Author Report Share Posted June 22, 2025 Been trying to get it started over the weekend with no luck. Tried charging the battery and checked all fuses but can’t find any issues. Getting 1 fault code which is p1570 Engine start blocked by immobilizer. I have also found on VCDS in the immo measuring blocks all numbers are 0 except 2 keys adapted and immo status 6. I’m going to check relay 109 and if that’s ok look at the immo itself but not sure what to do after that. Anyone got any ideas? thanks Quote Link to comment Share on other sites More sharing options...
mk2 Posted June 22, 2025 Report Share Posted June 22, 2025 Yeah, the immobiliser... There's a pick-up coil around the ignition key barrel. You could very carefully, remove the chip from your only working key and tape it to the pick-up ring. But you might already be getting a key symbol on the dash? Not sure if your version of GTi has it. Quote Link to comment Share on other sites More sharing options...
Tomandrew10 Posted June 22, 2025 Author Report Share Posted June 22, 2025 I’m thinking it’s more a power issue than a key issue, because if it was a key issue would there not be some response from the ecu to the immobiliser? I'm also struggling to find relay 109, I’m not sure if it has been replaced with a relay with a different number on it. There is a 95 which I’m not sure about all the others seem pretty normal. Do the positions of the relays vary from car to car? Thanks Quote Link to comment Share on other sites More sharing options...
mk2 Posted June 23, 2025 Report Share Posted June 23, 2025 You already have the immobiliser response code... it's the ECU that's given that code above, not the immob? Positions are the same, so you might be right. Might have been changed before? @lupogtiboy, do you have a relay position diagram? I can't find one for the Gti. 1 Quote Link to comment Share on other sites More sharing options...
Rich Posted June 23, 2025 Report Share Posted June 23, 2025 Does a GTi have 109? Location? 1 Quote Link to comment Share on other sites More sharing options...
lupogtiboy Posted June 23, 2025 Report Share Posted June 23, 2025 2 Quote Link to comment Share on other sites More sharing options...
Tomandrew10 Posted June 23, 2025 Author Report Share Posted June 23, 2025 That really helpful thanks!! I’ve seen some stuff saying p1570 is a hard code and is difficult to get rid of does anyone know anything about this? Originally there was a code about low voltage which went after the battery was charged so wondering if it just needs hard clearing. I’ve cleared the code on vcds but it just comes straight back so I’m wondering if it isn’t fully clearing it? Thanks Quote Link to comment Share on other sites More sharing options...
Tomandrew10 Posted June 23, 2025 Author Report Share Posted June 23, 2025 These are the codes that are coming up. Quote Link to comment Share on other sites More sharing options...
lupogtiboy Posted June 24, 2025 Report Share Posted June 24, 2025 Ross Tech Wiki shows this 17978/P1570/005488 - Ross-Tech Wiki and this for the other fault 18010/P1602/005634 - Ross-Tech Wiki 2 Quote Link to comment Share on other sites More sharing options...
Tomandrew10 Posted July 5, 2025 Author Report Share Posted July 5, 2025 Finally got chance to have another look today and decided to check the immobiliser, got it out and took the plastic covers off and there is a lot of corrosion on the board. There are multiple breaks in the tracks on the board which have been fixed but there may still be more which I haven’t found yet. I have tried putting the immobiliser back in but it still won’t start, I am wondering if the immobiliser needs resetting somehow to remove the block on the engine starting. Does anyone know if this may be the case? Also does anyone know if it’s possible to replace the immobiliser? Thanks Quote Link to comment Share on other sites More sharing options...
Rich Posted July 10, 2025 Report Share Posted July 10, 2025 Location? Quote Link to comment Share on other sites More sharing options...
Tomandrew10 Posted July 14, 2025 Author Report Share Posted July 14, 2025 Just though id put a post on in case anyone else has this issue. So the immobiliser had got wet at some point which had caused pretty severe corrosion on the plugs side of the immobiliser board. If the immobiliser is completely dead there seems to be 2 options, you can either replace the ECU, immobiliser and key chips with one from a different GTi, the other option is sending the ECU to someone who can decode the immobiliser off the ECU. I opted for the immobiliser removal option so i sent it to VAGTRONICS in Stoke, who decoded it very quickly and got it sent back same day! Car now works perfectly! Thanks for all the help! 3 Quote Link to comment Share on other sites More sharing options...
mk2 Posted July 14, 2025 Report Share Posted July 14, 2025 So what exactly did they do and how much? Good to know... Quote Link to comment Share on other sites More sharing options...
Tomandrew10 Posted July 15, 2025 Author Report Share Posted July 15, 2025 I believe they have just removed all the fault codes that involve the immobiliser. Cost £150 plus postage so much cheaper than finding an ECU immo and keys together and then fitting them. Quote Link to comment Share on other sites More sharing options...
mk2 Posted July 15, 2025 Report Share Posted July 15, 2025 So no immobiliser now? Means the keys will be cheaper to replace... 👍🏻 Quote Link to comment Share on other sites More sharing options...
Tomandrew10 Posted July 17, 2025 Author Report Share Posted July 17, 2025 Yep no immobiliser, i am going to hide a small switch that cuts the fuel pump just in case I'm ever parking in a dodgy area. Yep thats true, sounds like they are very pricey to replace with immo 3! Need to sort the leak that caused the damage to the immobiliser next! Quote Link to comment Share on other sites More sharing options...
John90 Posted August 3, 2025 Report Share Posted August 3, 2025 Pleased you got this sorted in the end. One less thing to go wrong on the car from now on. Keep the old immobox though as GTI's are so desireable and you or someone can swap the chips over to a used immo box. It will be a valuable collectors car one day! Very difficult to duplicate an immo box without the original. I bought a programming lead and learnt how to do immo off as we have a few Lupos, I now have a spare no immo ECU I can swap in for testing, along with a full set of known good relays. There is some interesting stuff in the original ECU like backup actual mileage, in addition to the mileage reported in the dash so good you didn't swap it out. 1 1 Quote Link to comment Share on other sites More sharing options...
Tomandrew10 Posted August 8, 2025 Author Report Share Posted August 8, 2025 Cheers! Yeah they do seem to cause some issues so glad its no longer a concern! Yeah kept hold of it just in case might have a look at getting it fixed further down the line but we shall see. Very glad i didn't have to swap anything over in the end as it seems like a right pain to do! Was good to take most of the driver side dash apart as well found some water down there from a leak above so i need to sort that. Hoping no relays fail as they seem like a pain to get too! 1 Quote Link to comment Share on other sites More sharing options...
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