Immobilizer problem

[pacemaker1000]

hi guys

i recently had a problem starting the car and got stranded.

all the lights were on and everything else looked normal and locking worked etc but car would not fire, battery was proved OK

having read some threads a changed the ignition switch but as it was not sticking before or causing any other problems i had my doubts and n ow suspecting the immobilizer

trouble is the fault is intermittent so i am reluctant to use the car

would the unit under the seat cause such a problem (i have checked for loose wires etc) or could it be the transponder or any other wiring/relays?

thanks in advance for any advice

ps car is a 2000my 2.7 manual

[mikefocke]

More info please

When you turned the key, did the key seem to go to the far right starting position?

When you did that, did you hear any sounds of a solenoid clicking, a starter motor turning?

What was the state of the gas in your tank?

Had you had any odd electrical issues prior to the incident where the car didn't start?

Was the steering wheel "locked" when you pressed on the key?

Clutch position? Gearshift position?

Edited November 13, 2010 by mikefocke

[JFP in PA]

Along with Mike, I'd take a look at the ignition switch, but also the clutch interlock switch; either can present the conditions you mention...........

Edited November 13, 2010 by JFP in PA

[pacemaker1000]

thanks for the quick response

when the problem is present:

the key works as normal and goes all the way and releases OK, all lights come on and there is no dimming of any lights. but engine will not fire!

there is plenty of clicking when the ignition position of the key is first selected but nothing when turning the final bit and certainly not from the starter!

everything else electrical works fine, locking/unlocking with remote radio etc

i am in the UK so we don't have to have the clutch depressed to start

the day it happened first i had just driven for 5 miles and pulled over for 2 mins when on return nothing happened. i tried for 20 mins unlocking car etc but nothing. when i returned an hour later with a meter to check the battery it just started and i drove it home with no problems

there was one time since when i had the key all the way over and held there that it fired after a delay of a few seconds and cant swear but i think its happened since i changed the ignition switch last night

anybody know if when the key is in the ignition does the immobilizer deactivate immediately or only when you try and fire up?

cheers

Edited November 13, 2010 by pacemaker1000

[Loren]

Key in the off position activates the airbag circuit only. When you turn it to on it activates the start circuit.

[pacemaker1000]

thanks

when you turn the ignition on and all lights come on what happens?

does the immobilizer activate then in preparation for the final turn to start?

reason i ask is because of the slight delay i sometimes notice when i try and fire up

[pacemaker1000]

having read other posts i should point out that i don't have any water leaks and the carpet is dry( where are the drainage points that your supposed to clear if this happens?)

i have removed and checked the Immobilizer connectors but not opened it

[RFM]

pacemaker1000, are you sure that UK cars do not use a clutch pedal switch ?

[pacemaker1000]

pacemaker1000, are you sure that UK cars do not use a clutch pedal switch ?

absolutely,

if the problem was the Immobilizer and it was breaking down would the car stall when driven. that is does the immobilizer only work on initial start or does it continually monitor the key?

[pacemaker1000]

took the battery off and checked the inside of the immobilizer and all looks ok

swapped the fuses around in the trunk

left battery off for good hour to reset electronics,replaced everything and gave car a run occasionally stopping and restarting when car was off the road

seems to be fine so fingers crossed it was the switch after all

[pacemaker1000]

well problem is back!

just tried to start car and with key held in start position it failed but fired a few seconds later!

when i retried it and held key again in start position it failed totally but fired once i had released it and tried again

so i got going but this really has to be sorted as next time i might not be so lucky and have the car at home

HELP!!

Edited November 15, 2010 by pacemaker1000

[pacemaker1000]

have called a couple of dealers who say its probably the IMMOB unit under the seat. although could be the key or IMMOB receiver in the ignition

no choice now but to change the IMMOB unit and keep fingers crossed. if it proves to be something else its tuff as the unit has tyo be bought from Porsche ( second hand will not do) and then programmed specifically for my car so redundant if it aint the problem

Edited November 16, 2010 by pacemaker1000

[pacemaker1000]

OK

i don't like things that don't make sense plus i am an engineer by trade and like to either fix things myself or at least understand what the problem is before i spend my cash

here's the deal:

in order to try and recreate the fault i decided to pull the 'start' relay in the boot thinking i would hear things clicking but stop the car from turning over all the time. this way i could abuse the ignition to try and reproduce the fault BUT i get exactly the same condition. same goes when i pull the DME relay.

now i am really confused as the fault could be almost anywhere in the loom on either of these circuits as well

i am still dubious of the IMMOB as pulling that kills everything electrical and have no other faults that would indicate it was failing

any ideas?

[zman1858]

If you click on the central lock on dash and it works and the remote lock work, then I feel the the imobli is fine, just had to change mine....the interior lights were flashing on and off, the remote lock won't work and central lock on dash do nothing...I would look else where

[pacemaker1000]

If you click on the central lock on dash and it works and the remote lock work, then I feel the the imobli is fine, just had to change mine....the interior lights were flashing on and off, the remote lock won't work and central lock on dash do nothing...I would look else where

Hi and thanks very much for the response and information

when it first happened, which lasted at least 30 mins, i successfully locked and unlocked the car with the remote but car wouldn't start

everything else worked also and like said i have never had any other electrical problems before or since so i tend to agree with you

i really want this to re-appear now at least long enough to try another key and some more diagnostics

i have also done some investigating on the start relay checking voltages. i removed the transponder from my spare key to get an appreciation of what the differences were between the IMMOB unit working correctly and not

to start, one side of the relay coil has 12v with the ignition on regardless of keys.

also the 'live' that is put through to the starter motor comes directly from the ignition switch(checked wiring diagram)so this is a good place to check if your ignition switch is working!

so the immob works by preventing the relay coil from energizing and passing the ignition live(which should always be there when key is turned all the way)through to the starter

this may be obvious to some but i thought it would be good to have this info should anyone need it

Edited November 17, 2010 by pacemaker1000

[pacemaker1000]

the fault re-appeared today for a brief 5 mins during which i was able to do some more diagnostics

12v from ignition OK getting to start lock rely(not the problem)

new key tried(not the problem)

no 12v going to starter (not the problem)

diagnosis: start lock relay prevented from activating by 12v on coil from IMMOB (pin 40 to be pricise on unit under seat)so now 90% this is the fault despite no other symptoms

in normal conditions the start lock relay has 12v on one side of its coil and 0 on the other with the ignition on and immob unit performing correctly ie relay 'made'

this chnges to 12v with duff key in ignition( transpnder pysiclly removed from key) OR my fault on ie relay 'open'

interestingly this 'test' point on the relay coil receives 12v when engine is running and also about 3-4 mins after key is removed

i doubt if i have given any information away to minimise the IMMOB function as i am sure this is not the only function of the immob unit to prevent the car from running

however the start lock relay is a good place to identify problems and proves the ignition switch (which could have saved me 20 quid had i known this before)and immob

[RFM]

Have you read this: http://www.renntech.org/forums/index.php?/topic/32022-car-wont-start-anyone-have-a-relay-diagram/ perhaps it helps.

[pacemaker1000]

its a simple task to bridge out the start lock relay with no ill effects. that way the immob signal has no effect

i am unsure as to whether this is the only fault/immobilizer on the car. if it pack up again tomorrow i will give it a go

[pacemaker1000]

more info for future reference:

when the key is left in the ignition for 2 mins it is NOT the immob that activates just the start lock relay!

if you bridge out the start lock relay the car will start and drive as normal. this feature must be there just to prevent accidental starting of the car.

also worth noting is that merely deactivating the ignition start position via the start lock relay is NOT the only immob on the car thank goodness or it would be a pretty easy workaround for a thief( proved this by inserting my dummy key, car will turn over but not fire)

so for my problem i will have to wait again for the genuine fault to return and find out if it is the actual full immob that is activating or just the start lock relay prevention circuit. if its the latter i will be happy to leave it strapped out

[pacemaker1000]

problem has not re-occurred since removing the relay and strapping it out. i have a meter permanently om the coil checking for the immob/engine run signal of 3.6v

its possible that it was the 12v standing on the other side of coil causing the problem

fingers crossed

[c337cc]

well problem is back!

just tried to start car and with key held in start position it failed but fired a few seconds later!

when i retried it and held key again in start position it failed totally but fired once i had released it and tried again

so i got going but this really has to be sorted as next time i might not be so lucky and have the car at home

HELP!!

Are you sure its not the electrical portion of the ignition switch?? That is a common failure before 03,the later ones fail too ,but not nearly as often. Early ones are no longer available from Porsche only from VW/Audi part # is4A0 905 849.If it is you switch I recomend you upgrade the lock assy to 996 347 017 07. It comes with the later style switch. I have done a ton of these.

Howard