When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Hi, I have just purchased my first ever Porsche. It is a 1991 928 S4 owned by a friend for 22 years and until 6 years ago was running well. It was put away for the winter and would not start the following spring. It has sat in the garage since then.
I suspect an alarm / mobiliser problem as it will fire up, run for a second or 2 and then cuts out after a chirrup from the alarm.
it has a sigma alarm and a cobra immobiliser.
the original receipt for the sigma dated 2000 had contact details who I rang but they no longer deal with Sigma and couldn’t help unless I took it to their workshop 60 miles away.
I would appreciate any advise as to where to start or recommendations for a specialist in West Yorkshire.
please see attached photos of wiring in the boot that is not connected, I have no idea if relevant but they are just loose.
Thank you for letting me join this very informative group and I hope to keep you updated with my progress as I work my way through the car.
Oh my - your best bet may be tracing those wires all the way to the CE panel and removing that aftermarket alarm system. Others will know better as to whether you can fix it and keep it in. Take a picture of your CE panel (in the passenger footwell behind the wooden board). It would be good to see what has been wired in there.
first step return the car to stock configuration,
remove all aftermarket electrical systems.
if you need help ask here,
or take the car to a 928 specialist.
resolder all the cut wires and heat shrink them
first step return the car to stock configuration,
remove all aftermarket electrical systems.
if you need help ask here,
or take the car to a 928 specialist.
resolder all the cut wires and heat shrink them
Thank you for your assistance. Is ok just to follow the wires and remove? I was concerned that this may permanently immobilise the car with some anti theft protection if I get it wrong.
wow this is a scary looking box of wires.
I have found the Cobra unit, see photos.
lots of spliced connections with tape.
would it be safe to just start and disconnect or could I permanently immobilise the car?
thank you all for your assistance so far.
I have also attached a photo of my car, yes it needs a clean, this is as found. The Cobra unit and connector Lots of spliced connections Earth point Cobra keypad,
Once you get this figured out (and I don't envy you that job) the good news is that you have a really pretty car, with great wheels and a cool interior.
If you are scared to just start ripping the alarm out, you might go through and document all the points where the wires are connected to the relay panel. The connectors that plug into the relay panel are named A(on the Left) through X, with I skipped. The wires in the connectors are numbered as follows:
Looking at any given plug connector, installed at panel,
Convention:with wires coming "out of the page"
15 25
14 24
13 23
12 22
11 21
(Credit: Landseer)
The late model wiring diagrams are around here, but hard to read. So if you post a list of all the connections the alarm module makes into the relay panel wires someone might be able to tell you which one is likely to be shutting off your car. Might be good to document also the colors of the wires coming from the alarm module. Someone might be familiar with that module and know what color wire does what.
At the moment it is not clear whether the alarm system is responsible for the start and then stop scenario or whether it is something else but the fact that the alarm system bleeps and then the motor dies is probably indicative.
Analyzing the stock system to see what is energised and what is not is really quite simple and as far as I could ascertain the stock system interdicts the energising circuit to the EZ relay [XXII] such that in the alarm condition the switched power supply [bus 15] is defeated. You can test for this by checking for voltage on contact 86 in the socket when the EZK relay is removed. To help you get an overview of the system see the attached sketch below that I prepared to help me when diagnosing the system- gets a bit confusing jumping around the wiring diagrams that you also need a set of.
Is your intent to remove that abortion of a system or is it to simply to get the thing running correctly? This is not clear.
Looking at the pics it would seem the system you have is programmable such that prior to starting you have to enter a discrete code the obvious question being whether you have the correct code combo. . As to what that system does to disable the car presumably is something of a "black hole". I would suggest that the first part of any analysis would be to jumper the three key relays- EZK, LH [XXV] and fuel pump [XXVI] across terminals 30 to 87 in the sockets - do them one at a time first and if that does not produce any results jumper all three simultaneously. Then feedback what you find. If the jumpers get the system running then defeating the alarm system temporarily should be quite easy.
If the system has multiple ways to immobilise the system then finding them all may well be very tricky and require a full audit of the wiring diagrams. This does not require a 928 specialist but would need a good auto electrician, preferably one with alarm system specialist knowledge and familiar with German wiring conventions. The wires with tape on them obviously give a clue.
As for any 928 knowledge base in West Yorkshireyou may well be scratching on that one- the Porsche centre in Leeds recently did a ground up rebuild of an S4 so presumably they would have some expertise available but as for their hourly rates....? No problem if you won the state lottery recently. The only UK based authority i might trust is Paul Anderson based in Stroud- I believe there are a couple of others scattered around the country.
No idea where you are located but presumably not too far from Mirfield or Bradford that I will be visiting in a couple of weeks time. Doubt I could help you directly on this one but always good to meet up with fellow 928 owners for moral suport if nothing else.
Finally, our 928 electical guru is Alan- his website is a treasure trove for anyone delving into this area and he has a downloadable PDF file explaining the system conventions that can be found here: http://www.928-electrics.com
At the moment it is not clear whether the alarm system is responsible for the start and then stop scenario or whether it is something else but the fact that the alarm system bleeps and then the motor dies is probably indicative.
Analyzing the stock system to see what is energised and what is not is really quite simple and as far as I could ascertain the stock system interdicts the energising circuit to the EZ relay [XXII] such that in the alarm condition the switched power supply [bus 15] is defeated. You can test for this by checking for voltage on contact 86 in the socket when the EZK relay is removed. To help you get an overview of the system see the attached sketch below that I prepared to help me when diagnosing the system- gets a bit confusing jumping around the wiring diagrams that you also need a set of.
Is your intent to remove that abortion of a system or is it to simply to get the thing running correctly? This is not clear.
Looking at the pics it would seem the system you have is programmable such that prior to starting you have to enter a discrete code the obvious question being whether you have the correct code combo. . As to what that system does to disable the car presumably is something of a "black hole". I would suggest that the first part of any analysis would be to jumper the three key relays- EZK, LH [XXV] and fuel pump [XXVI] across terminals 30 to 87 in the sockets - do them one at a time first and if that does not produce any results jumper all three simultaneously. Then feedback what you find. If the jumpers get the system running then defeating the alarm system temporarily should be quite easy.
If the system has multiple ways to immobilise the system then finding them all may well be very tricky and require a full audit of the wiring diagrams. This does not require a 928 specialist but would need a good auto electrician, preferably one with alarm system specialist knowledge and familiar with German wiring conventions. The wires with tape on them obviously give a clue.
As for any 928 knowledge base in West Yorkshireyou may well be scratching on that one- the Porsche centre in Leeds recently did a ground up rebuild of an S4 so presumably they would have some expertise available but as for their hourly rates....? No problem if you won the state lottery recently. The only UK based authority i might trust is Paul Anderson based in Stroud- I believe there are a couple of others scattered around the country.
Thank you Fred. For your time and help.
I am near Skipton in West Yorkshire and did try to to contact Porsche Leeds Classic services but after 2 calls i still have not had a reply, probably saved a fortune there.
The car was running before it was put away for the winter in 2016 and has not run since.
it has a Sigma key fob which opens the doors, once opened ignition turns on with the key but will not turn over. to start the car you have to present a Cobra fob to a red led contact and the it will turn over.
this all appears to work Ok. the car did run for a few seconds and then cut out with a corresponding Chirp from the alarm which is why i made the assumption that it was an alarm fault.
Since my post, when checking earth points i have had the same chirps when loosening ground points, so i might be looking in the wrong area.
the picture below shows a connection block. the Brown single cable was loose, as this was tightened the alarm again chirped away on each turn.
it is a strange connection with a blue cap tethered to it. there is no obvious place for the cap to go? loose brown cable and blue cap,
No idea where you are located but presumably not too far from Mirfield or Bradford that I will be visiting in a couple of weeks time. Doubt I could help you directly on this one but always good to meet up with fellow 928 owners for moral suport if nothing else.
Finally, our 928 electical guru is Alan- his website is a treasure trove for anyone delving into this area and he has a downloadable PDF file explaining the system conventions that can be found here: http://www.928-electrics.com
The "brown cable" is in fact a red cable that is probably knackered and suffering from "cable cancer". It is the main cable that powers bus 30 in the central electrical system, it is permanently live [i.e not switched like bus 15 and bus X] and if that thing earths you will instantly get a current flow north of 1000 amps that has the potential to burn down the car. The assembly is known as the "hot post" becuase it is always powered up. The 16mm2 "brown" cable should be the same colour as the two 10mm2 feeders on the other side- that it was loose tells its own story as any disconnect will stop the vehicle from running immediately. That bracket is meant to be hard fastened- there is supposed to be a plastic cover that prevents water ingress and the blue cap fastens to a stud on the side that is also live. if that is exposed and floating around -not good!
As I said there is a good chance you have more than one issue and that is what we see immediately. Thus the module you have fitted may well be an innocent victim- not the culprit horrific as all that insulation tape looks.
As for living in Skipton all I can say is I hate you with a vengeance! Believe it or not Skipton is on my planned itinerary as I plan to have lunch in that fish and chip restaurant next to the LL canal. When I was at University I used to love riding my BSA 650 round the Dales especially around Skipton, Hawes, Ribblehead etc etc- best biking roads in the UK bar non.
What you have shown on your photo is not the correct piece of kit by the way. That looks more like the connector that takes power to the ABS system located on the other side of the car. I suspect it is the correct bracket but someone has removed the central post and replaced it with a common or garden bolt thus there is nothing to mount the cap on- not a great idea!
The only problem i have here is that you have a UK spec right hand drive vehicle and i am not at all sure of the full scope of the layout differences. I will take some photos of my 928 to show how it should look.
Photos added:
Engine bay showing hot post location The correct type of hot post noting it has a "post". Note how the item is hard bolted to the body. The installation as it should look
05-09-2022, 11:10 AM
Hello and help please
