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E39 (1997 - 2003)
The BMW 5-Series (E39 chassis) was introduced in the United States as a 1997 model year car and lasted until the 2004 when the E60 chassis was released. The United States saw several variations including the 525i, 528i, 530i and 540i. -- View the E39 Wiki

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  #1  
Old 08-04-2011, 09:25 PM
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bkgreene39 bkgreene39 is offline
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Occupancy Sensor Advice

Hello to everyone i am new here, if this topic has been covered before then my bad; to anyone who replies thank you in advance. I have a 1998 528i, it appears to have an airbag light on. I have been told that it is my occupancy sensor in the passenger seat that is the issue. I looked up some stuff and i see people are selling and buying a device that can be integrated into the seat to trick the car into thinking that someone is sitting there. Let me know if this is a good idea, otherwise i heard it might be a pricey fix due to what im assuming the seat needs to be taken apart and what not. Anyone experience this before?
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  #2  
Old 08-04-2011, 09:36 PM
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bmw_n00b13 bmw_n00b13 is offline
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Best to fix it. It's one thing to use duct tape on your air intake, and quite another to duct tape a system that plays an important role in a crash situation. The car will see someone sitting there if the system is set up but the car will not operate the airbags in the most effective way.

In the meantime, the airbag system will still operate, but in a similar fashion to how they operate with an occupancy sensor faker in place; i.e. ignoring sensor input. So basically the device only turns the light off.

All airbag work must be done with the battery disconnected, or the light will be triggered. Airbags are explosive devices,&c., &c.
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  #3  
Old 08-04-2011, 09:51 PM
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so in the meantime even though i have the airbag light on that airbags will still deploy just not effectively? guess i gotta get this taken care of, kinda sucks though that i have to take my seat apart and replace the sensor
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  #4  
Old 08-04-2011, 10:11 PM
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airbags will deploy just fine if you use an resistor to trick the module, you will just get rid of the annoying light
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  #5  
Old 08-04-2011, 10:17 PM
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thanks guys
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  #6  
Old 08-04-2011, 10:19 PM
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If you use the module there will e little or no difference vs having the light on (aside from the light).

The occupancy sensor was installed for a few reasons, from underweight kids being in the front seat (won't fire the airbag) to insurance companies tired of shelling out extra cash for the majority of accidents (one driver, one or more unnecessary airbags).
There are notthat many cases of airbags firing while driving etc so I do trust BMW's airbag system and prefer it to manage the system unimpeded. You may find from your research that the benefits don't outweigh the cost, which may be true. This is just my $2. (after today's fun on wall street, 2˘ doesnt cut it!)
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  #7  
Old 08-04-2011, 10:33 PM
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We don't seem to get these threads all that often - so - I would ask the OP to keep us informed as to what is found - and - more importantly - what solutions are tried.

In the meantime, this is what we currently have in the bestlinks:

- What can cause an SRS airbag light (1) (2) (3) (4) (5) (6) & what tools reset the fault (1) (2) (3) (4) (5) & what happens when mechanics disconnect the airbag before the battery or they connect the battery before disconnecting the airbag in seat and window regulator repairs (1) (2) (3) (4) (5) & where to buy an airbag occupancy sensor bypass unit (1) (2).


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  #8  
Old 08-04-2011, 10:40 PM
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Quote:
Originally Posted by bkgreene39 View Post
airbag light on. I have been told that it is my occupancy sensor in the passenger seat that is the issue.
BTW, how was that diagnosed?

For example, how do we know that the airbag light isn't simply the result of someone disconnecting the brightly colored airbag connector incorrectly in the process of fixing a seat or a window regulator?

Just curious ... because ... if that's the case, the 'proper' approach is simply to reset the light.
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  #9  
Old 08-05-2011, 06:40 AM
alarmin alarmin is offline
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I did the 2 resistor and 1 diode trick I found online (YouTube video). Very easy to do and the airbag light did clear. From my research, the major concern is if you ever have small children sitting in the front passenger seat. With this fix the front passenger airbag will fire in an accident, even if a small child is sitting up front. We don't have any small children so it's not a concern for us, however, this repair is only temporary (for me) and once I get through all the other stuff on my repair / maintenance list I plan on replacing the seat pad.
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  #10  
Old 08-05-2011, 08:24 AM
cn90 cn90 is offline
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The idea behind this is that when placing an infant in car seat upfront, the sensor says "not enough" weight, so in a frontal collision, the airbag is not deployed.
This is because an air bag can knock the baby seat causing injury or death.

Since that time (1990s), the thinking has changed and the recommendation of most experts in the Health Care field (even the Academy of Pediatrics) recommends that most infants and children less than 40lbs should be in the REAR seat (and properly restrained).

My 1998 Volvo V70 does not have this stupid occupancy sensor.

To sum this up:

- It does not matter what car you drive, children less than 40lbs ---> REAR seats and restrain them properly.

- If I were you, your ghetto repair is a "permanent fix". Don't lose sleep over it.

You have "bigger fish to fry" LOL. Namely these are the items:

* Cooling system
* CCV, ICV etc.
* OFH Gasket
* Brake System Hoses/Seals
* Front Suspension Overhaul
* Rear Suspension Overhaul
* LCM issue
* FSR issue

etc. etc. etc.

And the list goes on.
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  #11  
Old 08-05-2011, 08:31 AM
cn90 cn90 is offline
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To re-iterate what I said above re American Academy of Pediatrics (AAP) recommendations, this is a useful link. I understand that we don't have children but you never know one day you may have to drive some kids (nieces, nephews etc.) around, and these are good guidelines to follow.

I have a simple rule: it does not matter what car I drive: kids less than 40lbs ---> REAR seat.


http://www.healthychildren.org/Engli...x?nfstatus=401


Quote:
Originally Posted by healthchidren.org
Never place a rear-facing car safety seat in the front seat of a vehicle that has an active front passenger air bag. If the air bag inflates, it will hit the back of the car safety seat, right where your baby’s head is, and could cause serious injury or death.
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  #12  
Old 08-05-2011, 09:03 AM
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Quote:
Originally Posted by bluebee View Post
BTW, how was that diagnosed?

For example, how do we know that the airbag light isn't simply the result of someone disconnecting the brightly colored airbag connector incorrectly in the process of fixing a seat or a window regulator?

Just curious ... because ... if that's the case, the 'proper' approach is simply to reset the light.
thats the thing a mechanic told me that was the case, whether or not he is correct i do not fully know. I am gonna bring it to a shop my friends father operates maybe i can get a clear cut answer.
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  #13  
Old 08-05-2011, 02:25 PM
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Quote:
Originally Posted by bkgreene39 View Post
maybe i can get a clear cut answer.
My suggestion (FWIW)?

Just have the SRS airbag light reset & see what happens next.
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  #14  
Old 08-05-2011, 02:43 PM
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Quote:
Originally Posted by bluebee View Post
My suggestion (FWIW)?

Just have the SRS airbag light reset & see what happens next.
Thanks for the advice, to be honest i wish i had the time and space to work on my car to see whats up with it, i love my e39 so much and the fact that im not working on the car if it needs work is killing me. I took it to my boys body shop to use his lift to do oil change, thats about it he doesnt know engines and electrical. I just got this car and want to take car of it.
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  #15  
Old 08-05-2011, 03:13 PM
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Quote:
Originally Posted by bkgreene39 View Post
the fact that im not working on the car if it needs work is killing me
I can't imagine how 'anyone' can afford these (now older) BMWs if they don't do the work themselves.

Trust me. If I can do it, anyone can.

Sure, you might make some mistakes ... but ... even with the mistakes, the cost will be far less than having someone else make those same mistakes at your cost of their time and bloat on the parts cost.

For example, here are just a few recent mistakes (not all mine, but most are mine) that were recovered from, with the help of the tribal members on bimmerfest:

- How not to repair your E39, by cn90 (1)
- How not to do an E39 gravity feed oil change (1)
- How not to do an E39 vacuum extraction oil change (1)
- How not to repair the E39 leather seat stitching (1)
- How not to remove the mass air flow sensor (MAF) spring clip (1)
- How not to remove the large radiator hose connector spring clips (1)
- How not to repair your E39 trunk wiring loom (1) [ how to do it right (1) ]
- How not to remove the nipple from the E39 radiator (broken radiator nipple)
- How not to put your E39 fan clutch back on (crooked fan clutch nut)
- How not to bleed your E39 cooling system (1) (broken bleeder screw)
- How not to replace your E39 thermostat (thermostat loom misplaced)
- How not to remove your E39 expansion tank (broken expansion tank nipple & cn90 repair)
- How not to replace your battery (1) (2) (3)
- How not to install rain sensors on the windshield glass (1)
- How not to remove the E39 MID (1) (2)
- How NOT to change the E39 battery (1) (2) (3)
- How not to install rain sensors on windshield glass (1)
- How not to replace your FSU/FSR (1)
- How not to replace your windshield wipers (1)
- How not to siphon gasoline out of your fuel tank (1)
etc.
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  #16  
Old 08-05-2011, 03:45 PM
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there are def things i will do but lets be realistic here things that require special tools\equipment for certain jobs are not exactly diy, my friend his whole family drives e39's, they dont even do everything themselves, the basic stuff i will be doing for sure without a doubt but in the end it all depends on what needs to be done.
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  #17  
Old 08-06-2011, 07:41 AM
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Quote:
Originally Posted by bkgreene39 View Post
things that require special tools\equipment for certain jobs
So far, my 2002 hasn't needed any 'special' tools other than a $40 set of counterhold & fan clutch tools (for the cooling system, alternator, & belt drive overhauls) - and - a 7mm allen wrench (for the four wheel brake job).

Other than that, no 'special' (i.e., out of the ordinary) tools were needed.
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  #18  
Old 12-15-2012, 04:20 AM
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I just ran a search for the airbag electronics locations for this thread:
- > E39 (1997 - 2003) > airbag light

When I ran into the following nice threads which are useful to others:
- > E39 (1997 - 2003) > SRS light fix. (Passenger seat mat) DIY
- > E39 (1997 - 2003) > Passenger occupancy sensor

Quote:
Originally Posted by xaff View Post
BMW installed these extremely sensitive mats under the seats, so if nobody is sitting on the passenger seat, the airbag will not deploy (saving repair costs). That is the ONLY purpose of the mat.

The good: Mat will save your airbag if no one is sitting in the seat, and you have a wreck. Saving you money (about $200 for the front, and / or about $150 for the side).

The bad: Anytime someone puts the knee on the passenger seat (to pick something up from the back etc) the mat dies. Anytime someone tosses something heavy, the mat dies. The darn thing is too sensitive. It costs $120, however putting it in is a real pain in the arse. It goes bad quick, and this money comes from your pocket. the post-wreck repair money comes from insurance guys pocket.

The decision: To hell with the mat. I'll jerry rig the thing.

So... I made a trip to "The Source" here in Canada. In US you'd have to go to Radio Shack. I asked the friendly gal behind the counter that I needed the following:

1. Qty 01 Diode - 1 Ampere.
2. Qty 01 Resistor - 56 K Ohm.
3. Qty 01 Capacitor - 100 Pico Farad.
4. I picked up a small connector block to put the resistors etc in.
5. Her phone number.


I Moved the seat up and look under it from the front. this connector was near the extreme rear, sticking out from the bottom. I moved the passenger seat all the way forward, and from the back seat (well, opening the rear passenger side door) I ran my fingers under the seat, near the back of it and found the connector.

I disconnected the battery and then unplugged the connector. I removed the portion that has white plastic piece sticking out. After that I put my fake weight simulator ( as shown in picture ) on the end of the wire and wrapped it in tape. I plugged it back in to the socket it came out of. The picture shows the actual thing, and the 'block diagram for non-techies'. I tried making it as simple (and childlike) as possible.

Also I was getting misc errors from driver seat side (belt switch, battery isolation etc ). I moved the driver seat all the way back and down and opened the connector's cover. I slid a sheet of plastic under the connector and liberally ( and I mean liberally ) sprayed contact cleaner on and in it. I noticed dirt dripping from it .. so I sprayed some more.

After resetting the light, viola .. no more SRS errors. Net repair cost .. I think $5 for the parts, $5 for the contact cleaner. I went for a little 'verification drive'.. I think I saw rainbows and unicorns... maybe it was the contact cleaner fumes.
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See also: E39 Bestlinks & How to easily find what you need
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  #19  
Old 12-15-2012, 09:17 AM
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bkgreene39 bkgreene39 is offline
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Wow I remember this thread, I first got my car and I was a fantastic noob. Ah the memories. I installed bypass device, and took it to an Indy so they can reset my airbag light.
Bluebee that info will be helpful to others.
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Last edited by bkgreene39; 12-15-2012 at 09:19 AM.
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  #20  
Old 12-15-2012, 01:21 PM
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bluebee bluebee is offline
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Quote:
Originally Posted by bkgreene39 View Post
Ah the memories. I installed bypass device, and took it to an Indy so they can reset my airbag light.
Thanks for reporting back.

For each unique issue on the E39, I used to link better thread after decent thread after good thread - but - now I simply try to pick an existing thread to make it the canonical thread - and link the other threads to it.

So that makes this thread the canonical thread on the E39 occupancy sensor repair.

That way, if we add something to this one thread, everyone gets the benefit.

To that end, nowadays, you can cheaply reset your SRS light at home:
- What is the cheapest usable BMW E39 airbag srs reset/scan tool on the net (1) & what other scan tools reset the fault (1) (2) (3) (4) (5) & a BMW description of the SRS system (1) & what can cause a BMW E39 SRS airbag light (1) (2) (3) (4) (5) (6) & a cn90 DIY for replacing the driver seat belt buckle pretensioner and the passenger seat emulator (1) (2) & where to obtain an airbag occupancy sensor bypass unit (0) (1) (2) & what happens when we disconnect the airbag before the battery or we connect the battery before disconnecting the airbag in seat and window regulator repairs (1) (2) (3) (4) (5) (6) (7) (8)
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Please read the suggested threads, where the best always add value to those threads, either by pictures or by descriptions, so the next person with the same problem stands on your shoulders.
See also: E39 Bestlinks & How to easily find what you need

Last edited by bluebee; 12-15-2012 at 01:26 PM.
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  #21  
Old 12-15-2012, 02:14 PM
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bkgreene39 bkgreene39 is offline
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I should have given an update way earlier. I guess better late then never. It cost me nothing to have the light reset at an indy, because I knew the guy and I helped him with computer repairs. Some of these posts I made on this thread reagrding work on my vehicle, too funny. Only until I started working on the car did I realize how straightforward it really is. Experience is the best teacher(along with diy articles)

Last edited by bkgreene39; 12-15-2012 at 02:15 PM.
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