96VR6NZ 2 Posted September 28, 2014 Report Share Posted September 28, 2014 Our 96 Golf VR6 auto (OBD2) will not start, it cranks but no spark.The ECU will not connect to my code reader or VAG - COM.I am pretty sure the ECU is buggered. Options are:1.Find one from salvage - which could also fail eventually- they are all the same age, capacitors and other components only have limited life in any electronic gear.2.Get a new one from VW - IF they still make them as replacement part and IF it is not too pricey.3.Find an after market replacement - perhaps performance enhanced. Your thoughts would be appreciated.... Link to post Share on other sites
Mk1 Vr6 james 103 Posted September 28, 2014 Report Share Posted September 28, 2014 What is the code on the ecu mate?Sent from my iPhone using Tapatalk Link to post Share on other sites
Mk1 Vr6 james 103 Posted September 28, 2014 Report Share Posted September 28, 2014 What is the code on the ecu mate?Sent from my iPhone using Tapatalk Link to post Share on other sites
turk 7 Posted September 28, 2014 Report Share Posted September 28, 2014 just check the ecu relay before hand iv had one go down on me before, that will give the same symptoms. MJ Vr6 1 Link to post Share on other sites
UnitedMotorsport 55 Posted September 28, 2014 Report Share Posted September 28, 2014 (edited) ECU # will be 021 906 256 OBD2 does not have an ECU relay. Just to add, Ive never ever seen any ECU fail that has not been molested in some way. Edited September 28, 2014 by UnitedMotorsport michael5556 1 Link to post Share on other sites
96VR6NZ 2 Posted September 30, 2014 Author Report Share Posted September 30, 2014 I booked it into the VW garage, they couldnt talk to the ECU either but suspect that the problem is the coil pack not the ECU. We shall see...... Link to post Share on other sites
UnitedMotorsport 55 Posted September 30, 2014 Report Share Posted September 30, 2014 The coil pack has no possible way to stop communication with the ECU. Link to post Share on other sites
michael5556 247 Posted September 30, 2014 Report Share Posted September 30, 2014 Are you sure it's not wiring, like the obd port wires have come undone? I've had that problem on a customers car. Link to post Share on other sites
96VR6NZ 2 Posted September 30, 2014 Author Report Share Posted September 30, 2014 I have not talked to the mechanic directly but I guess he is concentrating on the no-start fault and perhaps the ECU communication is not an issue. I will have to go down there and see what's going on. Before I took it to the dealership, I replaced the ECU relay and also checked the ECU fuse.I also confirmed that 12V supply is reaching the ECU.I could communicate with the SRS, ABS and Auto trans through the OBD port, so I think the port wiring is okay.The mechanic confirms that there is fuel but no spark. The HT leads were really bad and have been replaced.Before the no-start fault occurred the engine was a little lumpy on warm up but did not miss a beat when it was up to operating temperature. At this stage, they are trying to get a coil pack for me. Closest one is in Singapore! Link to post Share on other sites
96VR6NZ 2 Posted October 3, 2014 Author Report Share Posted October 3, 2014 It's not the ECU and it's not the coil pack.The car is still at the dealer, cranking but no spark.I found a second hand ECU, they fitted that, no spark, no start and still can't communicate with replacement ECU it via the OBD port.The new coil pack also made no difference.The VW tech says that he is getting pulses from the ECU to coil pack but still no spark.He has bypassed the engine earth with a jump lead direct to the engine from the battery negative.He found a broken wire on the immobiliser and thought he was onto it, but after repairing the wire we still have the same problem. So the saga continues ...... Link to post Share on other sites
michael5556 247 Posted October 4, 2014 Report Share Posted October 4, 2014 Did you check the k line for the obd port as that stops starting and communication with the ecu... Link to post Share on other sites
96VR6NZ 2 Posted October 4, 2014 Author Report Share Posted October 4, 2014 The k line? What are the pinouts of the OBD port?I really need a wiring diagram. I have electronics/electrical experience. With a wiring schematic I could probably have a go. Is there anything available online?... A wiring diagram please guys... showing the ECU and immobiliser. Thanks Link to post Share on other sites
michael5556 247 Posted October 4, 2014 Report Share Posted October 4, 2014 http://www.a2resource.com/electrical/management/motronicvr6aba.htmlPin 43 from ecu. Grey/white Link to post Share on other sites
96VR6NZ 2 Posted October 4, 2014 Author Report Share Posted October 4, 2014 OKay thanks Michael I see that on the pin out for the EU socket... grey/white.pin 43.. good to know.But how does it work?. what's the normal and what's the fault condition? does pin 43 pair to earth or is it and earth switch/signal? Link to post Share on other sites
michael5556 247 Posted October 4, 2014 Report Share Posted October 4, 2014 No there is a plug between the ecu and obd port Link to post Share on other sites
96VR6NZ 2 Posted October 5, 2014 Author Report Share Posted October 5, 2014 Where is the plug? it's a good place to test from Link to post Share on other sites
michael5556 247 Posted October 5, 2014 Report Share Posted October 5, 2014 It's a small one pin white plug. If that plug is disconnected then the car will not start and you won't be able to talk to the ecu. Just follow the wires behind your dash from the obd port Link to post Share on other sites
96VR6NZ 2 Posted October 6, 2014 Author Report Share Posted October 6, 2014 I passed that info onto the VW tech yesterday. He traced the wiring back from the OBD port and it is all okay. Still can't talk to the ECU and cranks but no start. He thinks that not being able to talk to the ECU via that OBD port also means that the ECU and Immobiliser can't talk to each other. He reckons the immobiliser is the next thing to try, we have ordered a replacement unit. Should arrive today. Link to post Share on other sites
UnitedMotorsport 55 Posted October 6, 2014 Report Share Posted October 6, 2014 If that were the case, the engine would start and run for 1 second and then turn off. Link to post Share on other sites
michael5556 247 Posted October 7, 2014 Report Share Posted October 7, 2014 I'm telling you it's that wire lol I can't say it enough. It's a white plug. If it's not that then you have some serious issues. As United says, it would run for a second then cut out. Plus even if it was the immobiliser then you would still be able to talk to the ecu nd it would come up with fault codes Link to post Share on other sites
96VR6NZ 2 Posted October 7, 2014 Author Report Share Posted October 7, 2014 It's sorted and back on the road.The immobiliser unit was replaced and full communication with the ECU was restored. Somehow the immobiliser was blocking the comms with the OBD port. The tech says that the diagnostic signal passes through the immobiliser. Still no start and no spark at this point, so he changed the coil pack it she started up with no fault codes. The ignition switch also caused issues with no cranking at all at one point. So to summarise, multiple faults: The immobiliser unit was faulty, blocking the ECU comms with the OBD port and possibly causing other issues. The coil pack was faulty, no spark.And the ignition switch failed during the fault rectification causing no cranking. I suppose with these things it's always possible that several things can fail at the same time, it was a tricky one. Hopefully we have got all our troubles out the the way in one hit! Thanks for your ideas guys, I learnt a lot. Cheers Link to post Share on other sites
96VR6NZ 2 Posted October 9, 2014 Author Report Share Posted October 9, 2014 We got it sorted finally.Replacing the immobilser control unit restored the communications at the OBD port, apparently the diagnostic connection goes through the immobilser.The ECU was re-coded but still cranking with no start.The coil pack was changed and she started up. No trouble codes in the ECU. So to summarise, the problems were caused by three components becoming faulty at the same time. The ignition switch, the immobiliser control unit and the coil pack.2 days labour plus parts... ouch. She was going great for a day until the MAF sensor failed, but that's a different story.... Thanks for your ideas and suggestions guys, I learnt a lot. michael5556 1 Link to post Share on other sites
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