996 non starting

I have a 1999 996 C4 which all the ignition lights come on but it does not turn over. Its not the battery and if you remove the starter relay under the back seat you can bridge out the relay contacts and turn the engine over with the relay removed and get the engine to turn over. so this proves the ingnition switch as well. Its not the key as either. so my thinking is its the imobliser system or DME controller. the fault started with it becoming hard to get to turn over over a few days now it just does not turn. you would turn the key and noting happens we have checked all the relays under the back seat and moved them round and checked for corrosion etc . Do these have a DME relay like the 993's or it controlled through an ECU? Has any one had issues or problems with these. Thoughts appreciated.

Have you checked the earthing points? Sounds like there might be a deterioration going on there, not a switch-of, if you see what I mean?

yes I see what you mean, its certainly something is not sendind the power command to the Start block relay, but I donnt have a full wiring diagram for it, Earth I have checked so far as I can find them. Thanks for the reply

Manuals are here .. http://911uk.com/viewtopic.php?t=83491 Relays are here .. http://911uk.com/viewtopic.php?t=77063 Relay board 2 has the closest to a 993 dme relay but it lasts a lot longer lol . If you bridge the starter relay it should start .. if it doesnt then it sounds like an imobiliser fault .. would need a tester to confirm . Check under the n/s/f seat .. alarm unit is there .. its prone to getting wet and will cause all sorts of problems .. i would start here as its this i feel maybe the fault. If you want to remove it you will need the battery disconnected .. ign on then disconnect the battery or the alarm will trigger. You can remove the alarm cu with battery still connected but again would need ign on to stop it triggering .. battery off is safer .

Many Thanks I will get the seat out and see whats going on.

ok seats out and controller removed, it triggers the alarm, as expected, when disconnectet so looks like there is conectivity of some description, wiring is clean intact and no sign of any moisture or wiring damage, next Port call needs to the the ingnition lock side of things, looks like a oig to remove1 Then will likley buy a matched set of the ingnition lock and 2 X Ecu's as test set Ex E bay as there is plenty availability and there not expensive. Having checked and wiggled all the realays swapping the 3 elements is likley a good starting point then if that does not spark it us its pin to pin with the wiring drawings.

With a tester on the vehicle you can see if its in alarm state or not .. you could also see dme codes which in turn may tell you the fault .. So a fault code check and actual values check might be a cheaper option . If your replaceing control units then you would have to replace the dme and the alarm control unit .. you would also need an alarm key fob coded to them for that swop to work. With out the chassis number of the car that those items come from you would never be able to code on another key fob . IPAS codes ( to code on a new key ) are related to the chassis number . Disconnecting the alarm cu with ign off will trigger the alarm as mentioned. The purpose of this is to look inside the black box for corrosion .. if nothing then its probably not at fault .. again a system doesn't just fail on the immobiliser side .. theres a reason for it .. power / earthes to either unit need to be checked . Ignition lock replacement is sensible .. you can get unusual faults from that .. But not starting is not one ive seen before . Ign lock replacement is actually pretty easy .. just looks hard .. Remove instrument cluster , x2 screw behind hazard light cover / switch and behind vent cover o/s .. remove headlight switch and air vent , remove cover under cluster , remove 10 mm bolt and wireing plug , remove bracket from behind air vent .. Push in the lock button underside of the ign lock assembly with key in ignition pos 1 then remove . To get the barrel out i use an oxy / accetalyne cleaning kit .. small round files for cleaning the nozzles .. you slide it into the hole in the chrome section .. press in and it will release the barrel lock .. have to line up the holes first though .

error codes: 21 no engine start possible W Lead (DME immoblizer) open circuit status: present number of times DTC present 5 60 Central locking limit position Locked switch for central locking is faulty Stautus Not Present Number of Time DTC present 3 (central locking is working)

fault code pictures

You do indeed have an imobiliser fault . The remote part of the fob unlocks the vehicle but its the transponder pill in the key head that is read through the ignition that disables the imobiliser and as such it might just be a fault with the key head , maybe code on a new key if possible or see if you have a spare one . I have seen one problem which was actually the reader that was faulty .. its a black box fitted to the ignition lock . Could also be the windings in the ignition lock .. but never seen that before. Another point to check would be actual continuity of the W lead wire .. and i seem to rembember a K lead wire which is also part of the alarm system .. might be a diff Porsche though. Other than that then standard checks on both control units .. earths .. feeds etc. Thinking about changeing both control units .. if no chassis number then ive herd its possible to clone a key but not something ive done before .. i just code them the standard way. Once you have it running though you need to check the engine sensors .. might be rodent damage there .. coolant temp fault will certainly give you running faults .

Thanks again for the feed back, I tink I am going to go OPC to get them to try to code a new key and see what there thinking is on it, spending 2-3 hours with them might be the best option, once i check all the earths and obvious wiring loom checks.

Pig of a thing now runs! Having had all the relays out and swapped round, (again) where you can and all the connections off, (again) and sprayed with contact cleaner its running now. No specific reason or fault, so I will clear down the fault codes and run it and see what codes come back then revisit what to do next. annoying not to have a definitive cause but that's the joys of electrical faults. :nooo:

how old / battered is the key ? do you have more than one ?

Unfortunatly i have had that happen several times , its also possible disconnecting power to dme / alarm might kind of reset it and get it working .. same as turning it off and on basically. Plus side though is it runs Have a look for that coolant temp sensor fault though .. you will get start and or running problems if thats a permanent fault.

Quotes source post: 990527

Thanks deMort Swapped my key body yesterday because the sides had seperated and wouldn't reconnect. Went to start the car this morning and .. nothing .. not even a click. I had left out the imobiliser pin and your post here pointed me to that.