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Help Needed - Mobiliser Problem

2K views 12 replies 6 participants last post by  Spidercrab 
#1 ·
I have a 1997 E36 318i Touring SE UK spec that has developed a very strange electrical fault.

About 6 months ago, I noticed that the Outside Temp display and digital clock were not working when I was driving along. When I reached my destination, I checked the fuses and everything was OK. However, the car refused to start. The ignition lights were lit and I could hear the fuel pump, but it would not turn over. I called the RAC (Auto rescue) and they could not start it - we even tried a tow start. While waiting for a tow home, I tried to start the car and the outside temp display and clock were now working and the car started OK. I drove to my BMW garage and they could not find a fault with it. It does however, have a sticker on the rear windows for a Sigma Car Alarm, even though I don't have a Radio Key for it and the LED light that I assume is the Alarm Active LED never lights. I have always assumed that the Alarm is off or perhaps removed. The garage thought that there may be an alarm and sugested having it removed in case there was a fault in the alarm. I decided not to have it removed (not sure if there is an alarm anyway). It has run perfectly since until today when I had the same fault.

I just couldn't start the car. I noticed that when the ignition is on that the outside temp, digital clock, electric windows and sunroof do not operate. Central locking works fine. I called the RAC again and after about 1 hour the guy said there was no 12V on fuse 45 which is the imobiliser fuse. He temporarily connected 12V to the fuse 45 and I could start the car. With 12V on fuse 45 the outside temp and clock functioned. The 12V was removed from fuse 45 and the engine continued to run so I drove home without any problem except that the windows, sunroof, instrument panel temp gauge, outside temp and clock did not work. I have tried my second key but that still does not work.

This seems to be an imobiliser problem or if there is an alarm then perhaps the alarm is faulty and is imobilising the car, However, I can't find an alarm box anywhere!

So. Does anyone know if this is a know fault?
Could this be a relay problem?
Any suggestions on how to cure this?

Any help on this would be so much appreciated.

Gary
 
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#2 ·
First off... if you think there is an alarm... probably stock... then remove it.. or get it removed.. and see if that helps your situation... as for the imobiliser problem... many car alarms tie into that system... and many dont... most of the higher range alarm systems tie in ....

If you dont have the fuse in place for the system.. then its going to default to its locked position... best bet... replace the fuse... and see if she works normally...

As for the other things such as your sunroof.. windows... ect. that dont worry.. there is a relay that is devoted to comfort... and those things are a part of that... research where your comfort relay is... and either check that or get it checked out... this is a common problem.

Good Luck,

Les
 
#4 ·
For the imobilizer unit.. there is the processor... which is partially behind the glove box... and right around your left foot sites while driving... as for the other things there is the ignition sender which sends the signal from your key through the antenna to your processor to be processed as either valid or invalid... then once your processor says its good... it allows ignition to take place by sending power to your ignition relay.

The confort relay and the EIS (electronic imobiliser system) have nothing to do with each other... two different systems...

Good Luck,

Les
 
#6 ·
There are two fuses for the immobilizer, one resets the clock and something else and disables the car, the other one disables the AC along with the rest of the car :p
That's all I know about for sure... That plus everything les said.

It is possible that the sticker is there as a visual deterrant and nothing else... It's also possible that a wire is loose to the 45 fuse or there is a box hidden in-line with that wire to the fuse that is breaking the connection (IE: that alarm your talking about).

If you decide to MAKE an immobiliser switch, don't use 45 where it turns off the clock, use the other one that disables the AC as well. As you can see, all you gotta do is stop 12V from reaching that fuse (and use a switch rated for at least 7.5 amps [or whatever the fuse is, I think it's 7.5 offhand] or get a small 12V relay fed from another fuse)
 
#7 ·
I helped out jrhaile at one time through a maze of electrical diagrams in a ETM (electronic troubleshooting manual) due to the fact that is EIS went hywire... there are a few other components... and most of these components you and find location and purpose in a Bentely manual...

Just so ya know...

Good Luck,

Les
 
#8 ·
I have investigated the alarm and there does not appear to be an alarm fitted.

I took the car to my local independant BMW garage and they confirmed that there is no alarm. They did a diagnosis and found 2 reported issues. One was an unknown error that they knew fom experience to be Anti theft alarm fault - and this is related to the second fault which was Wrong key used. Unfortunately, when I got to the garage the fault fixed itself, and the windows, roof, temp display all worked and the car would start fine!!!!!!

They thought the problem was probably 2 things.
1. The key could be faulty. However, as I have tried my second key with the same result I don't think this is likely.
2. They said there is a know problem with water leaking into the ECU unit mounted under the fuse box and this may be shorting some wiring out. To fix this means dismantling of the ECU and possible replacing - ouch at about £400 parts cost.

I think this could also be caused by a faulty key switch that fails to recognise the correct key. Clearly the right key has always been used but something on the key side registered otherwise.

Anyone know what happens when a wrong key is used? Does the ignition switch on but starter not workt?
 
#9 ·
This problem is occuring again and driving me crazy.

There are several new symptoms that I have noticed.

The car will work perfectly until I notice one or more of the following when I am driving:
1. The inside lights will come on.
2. The Airbag light will come on for a few seconds and go off.
3. The Fuel gauge will drop to empty anf the low fuel light will come on for a few seconds.
4. The outside temp and engine coolant temp will die.

After this event the outside temp will remain dead for the duration of the problem. When this happens the following do not work:
Windscreen wipers, brake lights, map lights.
The following have also stopped working but have worked on other occasions:
The windows and roof.

When the fault condition exists the car will not start unless I put the ignition switch to the first position, touch fuse 45 with +12v for a short time and then start with key as normal. I can then use the car except without windscreen wipers and brake lights, this is far from ideal, i.e. bloody dangerous.

I had thought that the problem was due to the key so I have been carrying my 2 keys with me. Occasionally, the car would not start and I would just repeadedly try each key and it would usually start after about 20+ attempts at this. Once started it would work perfectly.

Now that the weather is much more damp than during the last 6 months, I think it is significant that the car is playing up. I have yet to find the DME. The car being right hand drive has the DME located behind the battery and fuse box on the passenger side - I think. However, it looks like the fuse box will have to be removed first which looks difficult.

So I have some questions that I hope someone here may know the answers to:
1. I have read about the DME getting wet on these forums and wonder if this could be my problem. Anyone know how to check the DME on a right hand drive car?
2. I suspect the immobiliser is causing the problems. As I understand it, the correct coded ignition key will enable some sort of RF sender in the key switch which sends an RF signal somewhere to say go or not. How can I check this process?
3. Does anyone know how an E36 would behave if the wrong key was used? This would be the senario that the car sees if the key switch is faulty. Specifically I would like to know what dashboard and instrument lights would show or not show. Is there, for example, a visual signal that the wrong or a damged key has been used?

I am really reluctant to give the car to a BMW garage to diagnose as I see this sort of problem as a license to print money.
 
#10 ·
The water on the ECU explanation I believe is bogus. There are some really old threads about that happening and I recall the syptoms to be the car either working or not working, not your cars werid half way working. But you can check and see if you have the potential for water damage to happen, by looking at the corners of your hood cowl. If the corner is missing on the side with your ECU then there is the possibility for water to make it to your ECU. Also does does it rain, snow or washing your car, occur just before this happens?

As far as the wrong key, it should not be the case that you could use a wrong key with the car for such a long time. The keys are laser cut, if there is any difference at all it will wear out the locks and ignition (the parts you put the key into). So I am reluctant to blame the key for the problem.
 
#11 ·
thekid said:
As far as the wrong key, it should not be the case that you could use a wrong key with the car for such a long time. The keys are laser cut, if there is any difference at all it will wear out the locks and ignition (the parts you put the key into). So I am reluctant to blame the key for the problem.
By wrong key I meant "wrong" as in the sense that the T/R module thinks the key is wrong. The 2 keys that I have are the correct keys and both can be used as normal to start the car 99.99% of the time. But I suspect there is a intermittent fault somewhere that might be caused by the key barrel, conductive loop and T/R module thinking that the key inserted has the wrong code and the RF signal to say we have lift off, does not get sent.
 
#12 ·
Test your key

One way of testing the chip in the key is to wrap the plastic part in tinfoil, (this screens the chip from the coil around the barrel) then try and start the engine. All the lights come on as normal, but there is no response at all from the starter. I have heard that the coil around the barrel can go intermittent, and cause all sorts of wierd problems, especially with things that would normally be on with the ignition. If you use a key with a dud chip, the same will happen, it shouldnt do any harm.
A genuine Sigma alarm has a small number pad (mine is on the windshield by the mirror.) so you can enter a pin number if you dont have your radio fob.
 
#13 ·
I just wanted to close this off with the solution to this problem.

The problem was caused by a hairline crack in the back of the ignition switch that fed power to Terminal "R". Thinking back on the symptoms I can now see how this was causing the problems I was having. The solution was just a low cost replacment of the terminal part of the ignition switch.

What I found very frustrating along this long path trying to solve this problem was the number of incorrect solutions that were offered by different BMW and independent BMW garages. They basicly seemed to cover changing the keys, antenna ring, RF module, EWSII module, engine management system (even though the engine ran perfectly throughout the problem periods), modifying the bulkhead to cure water leaks, removing an Alarm that wasn't present in the car and all of them included an expensive diagnosis which did not register the fault.

The solution was found by Promotive in Risca, near Newport, South Wales (UK). I just cannot recomend these people more highly.

Many thanks for all the suggestions along the way.
 
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