9025 Component B48 (Front Passenger Seat Occupied and Child Seat Recognition) is Defective. W211 E55

[pmcgsmurf]

Hi folks

Error Code 9025 Component B48 (Front Passenger Seat Occupied and Child Seat Recognition) is Defective W211 E55

I can't seem to get a break with this car, fix one thing then something else goes.
Seen this error today but only when someone (adult) is in the passenger seat.

Anyone seen this error on a W211 E55 and got any pointers to repair before I start pulling things out?

In particular if there is a way to test the Seat Pad Sensor whilst in the seat that would help me either diagnose this or eliminate it.

On a plus note after repairing the Keyless today it's the only error being shown on Star.

 

[pmcgsmurf]

Anyone?

Checked all the plugs and wires and seem ok.

 

[Codger49]

Bit of a pain, this one.

There's a sensor pad matrix inbetween the layers of the seat. Seat out and strip down job to get to it and replacements aren't cheap.

Ebay have little box gubbins that you plug in and it provides a false seat occupied signal to the SRS control unit. Danger with these is that a child seat will not be recognised and the passenger dash airbag will always go off if motion sensors trigger. It needs to be a 'gubbins' as the occupied/not occupied signal is a coded handshake.

Can be used as a workaround if you are certain of not using a child seat on the front passenger seat.

Mercedes SRS seat emulator | eBay

 

[markjay]

Yes, it's the Front Passanger Seat Occupancy Sensor, that is supposed to prevent the passanger airbag from needlessly deploying when the front seat is unoccupied.

It was £140 for the part, and one hour labour (removing and dismantling the front passanger seat) on my W203 C-Class.

Hope thos helps.

 

[pmcgsmurf]

Thanks. ^^

Might pull the seat out tomorrow for a look, at least that is only 4 bolts and a lot of plugs.

Anyone got a wiring diagram?
Shouldn't be that much to the sensor, would be good to see how it functions.

Checked the part number and it's A2118700410 but don't see any for sale online.
I've also got a W211 E220 with which says it has A2118211958 fitted, wonder if they are the same and I could swap to test?

Take it these are Bosch, anyone know the Bosch part number?

 

[pmcgsmurf]

Thought I had this sussed today.

Unplugged the sensor plug, plugged this back in and ran the car for 3 journeys in the morning, no SRS error.

Then jumped in car to go get lunch and immediately the error appeared, seems to be a bit intermittent though.

 

[markjay]

When my sensor mat went, this is what it did, i.e. the SRS warning was intermittent. Replacing the sensor mat sorted it for good.

 

[pmcgsmurf]

When my sensor mat went, this is what it did, i.e. the SRS warning was intermittent. Replacing the sensor mat sorted it for good.

Thanks, I'll see what price a new one is on Monday.

 

[pmcgsmurf]

Wow, £360

I'm flabbergasted.

 

[pmcgsmurf]

Anyone know what would be involved in coding the AKSE out of the system?

I'm guessing it needs done in a few control modules.

 

[andy27168]

Hi,
I have fixed 5 cars now with this issue my Audi A4 B7 Cab, a 06 plate VW Passat, an Audi S4 B6 Cab and 2 Mercedes ML's (X Plate and a 04 Plate), every one was the same issue dodgy electrical connections, SRS/Airbag light coming on/off.
I isolated the specific seat sensor pad connector, unplugged it and disassembled both connectors, the pins from the plug I wiped down with electrical cleaner, the sockets of connectors I gently squeezed them with pliers to make the pins a tighter fit, check fitted the pins in their respective sockets to ensure a tight interference fit, re-assembled the plug and socket plug it back in and cleared the code if necessary.
The SRS/airbag light has stayed out on everyone so far fingers crossed.
If you decide to try this route do make sure you take note of the positions of each cable in the connectors, and if you haven't got a means to clear the light avoid turning on the ignition.

 

[markjay]

It is definitely worth trying to clean the electrical connectors at the base of the seat, but the issue on Mercedes Benz cars is usually the sensor itself so in most cases the cleaning does not resolve the issue.

There are cheap SRS emularors on eBay that plug into the loom (instead of the seat), and trick the SRS ECU into thinking that the seat occupancy sensor is present and that the seat is occupied. Personally I would never install such a device on the SRS system... but apparently many people do, probably due tp the high cost of the sensor mat.

On another note, whichever way you modify the SRS system, i.e. by writing-out the AKSE system using STAR or by fitting a £15 emulator, you should notify your insurer or risk having your policy void... and I have no idea how the insurer will respond to a declaration of DIY SRS modifications.....

 

[markjay]

mercedes srs emulator | eBay

 

[pmcgsmurf]

I have fixed 5 cars now with this issue my Audi A4 B7 Cab, a 06 plate VW Passat, an Audi S4 B6 Cab and 2 Mercedes ML's (X Plate and a 04 Plate), every one was the same issue dodgy electrical connections, SRS/Airbag light coming on/off.
I isolated the specific seat sensor pad connector, unplugged it and disassembled both connectors, the pins from the plug I wiped down with electrical cleaner, the sockets of connectors I gently squeezed them with pliers to make the pins a tighter fit, check fitted the pins in their respective sockets to ensure a tight interference fit, re-assembled the plug and socket plug it back in and cleared the code if necessary.

Thanks, I'll give this a try, may have to end up removing the seat to get to the connector though.

 

[pmcgsmurf]

It is definitely worth trying to clean the electrical connectors at the base of the seat, but the issue on Mercedes Benz cars is usually the sensor itself so in most cases the cleaning does not resolve the issue.

Will certainly give this a try, I've had the plug out but not stripped it to clean it.

Likely need the seat out for this though, good excuse to clean under it but then I need to do the same to the driver seat!

There are cheap SRS emularors on eBay that plug into the loom (instead of the seat), and trick the SRS ECU into thinking that the seat occupancy sensor is present and that the seat is occupied. Personally I would never install such a device on the SRS system... but apparently many people do, probably due tp the high cost of the sensor mat.

Yes, does seem a common problem and the cost I was quoted today is mad.

On another note, whichever way you modify the SRS system, i.e. by writing-out the AKSE system using STAR or by fitting a £15 emulator, you should notify your insurer or risk having your policy void... and I have no idea how the insurer will respond to a declaration of DIY SRS modifications.....

When I was reading today I read somewhere that after 2006 (?) the AKSE system was disabled and the passenger airbag would always operate (if triggered ) if the seat was occupied.
I found a WIS document about this which was why I asked, need to see if I can find that one again.

On checking with the parts guy today about the possibility of using the facelift part number A2118701510 it got a bit confusing:

Part number A2118700410 is listed twice, one with codes 805 and U18.

The other 805 and (-U18), the minus sign meaning it shouldn't be on the datacard.

The datacard does not have U18 but one of the part numbers are listing it as okay for U18, then to make matters worse and more confusing, the facelift part number lists as good for codes 805 and U18 also, normally face lift model parts would have a different year of manufacture code (805, 806 etc...)

The facelift part number is "only" £168 so getting closer to worth a try.

My brain is now getting frizzled.......

 

[pmcgsmurf]

I found the document, GF91.60-P-4035T attached.

It says:

"As of 1.6.05 the weight classification of the front passenger is omitted."

Unless I'm missing something?

 

[markjay]

I found the document, GF91.60-P-4035T attached.

It says:

"As of 1.6.05 the weight classification of the front passenger is omitted."

Unless I'm missing something?

Reading the document, my understanding is that the way the sensor works has changed, but the sensor itself has not been omitted? I.e. the seat still has a sensor mat which determines how the SRS is deployed?

 

[markjay]

Are there no second hand alternatives from eBay? Perhaps even a complete seat (even if in poor condition) from which you can remove the sensor mat?

 

[pmcgsmurf]

Reading the document, my understanding is that the way the sensor works has changed, but the sensor itself has not been omitted? I.e. the seat still has a sensor mat which determines how the SRS is deployed?

Seems to be, but no mention of weight now so to me it would appear that on the later model facelift it should be OK to omit the AKSE coding, not 100% clear though.

 

[pmcgsmurf]

Are there no second hand alternatives from eBay? Perhaps even a complete seat (even if in poor condition) from which you can remove the sensor mat?

Not found any with the correct part numbers.

A seat/cushion may be an option but I had buying used parts that are of unknown condition, nothing worse than fitting a part and still having the same problem!