Passenger Seat Occupancy sensor
Discussion
I've posted this in the readers cars section as well.
My 12c has an airbag light due to the passenger seat sensor failing. The original cars had weird load sensing bolts which are no longer available so the fix is to detriment the seat and fit a regular weight sensing mat just like every other car on the planet.
However they no longer can get the parts and so McLaren have ordered a whole new seat as vast expense (£14K under warranty luckily). This has been on back order for 4 months....
Does anyone know of where to get the mats, or if there is another way of bypassing the system? (I'm not planning to put children or car seats in it) I imagine there might be a fix involving a couple of resistors or something.
The guys at V-engineering didn't suggest any alternative (super helpful guys by the way, it's definitely gong there once out of warranty.)
The car is just amazing though, so fast and planted and with the inconel sports exhaust it even sounds good too, I had not expected that. Track tyres are going on soon and then to Silverstone, can't wait!
(It's also just gone back t the dealer as I parked it nose down in a rain storm one night and the oil sender has flooded. The replacement is raised a bit to prevent this happening again. Good thing for the warranty!)
My 12c has an airbag light due to the passenger seat sensor failing. The original cars had weird load sensing bolts which are no longer available so the fix is to detriment the seat and fit a regular weight sensing mat just like every other car on the planet.
However they no longer can get the parts and so McLaren have ordered a whole new seat as vast expense (£14K under warranty luckily). This has been on back order for 4 months....
Does anyone know of where to get the mats, or if there is another way of bypassing the system? (I'm not planning to put children or car seats in it) I imagine there might be a fix involving a couple of resistors or something.
The guys at V-engineering didn't suggest any alternative (super helpful guys by the way, it's definitely gong there once out of warranty.)
The car is just amazing though, so fast and planted and with the inconel sports exhaust it even sounds good too, I had not expected that. Track tyres are going on soon and then to Silverstone, can't wait!
(It's also just gone back t the dealer as I parked it nose down in a rain storm one night and the oil sender has flooded. The replacement is raised a bit to prevent this happening again. Good thing for the warranty!)
I would advise either,
Getting a 2nd hand seat to match, or a damaged 2nd hand seat and remove the sensor pad.
Or
Buy a set of more modern 720s/570s etc seats as by all accounts they are more comfortable, Thorney did a video on the swap
I remember reading something about this on Mclarenlife which covered the issue with the older seats.
You won't be able to use a resistor, apparently Mclarens have variable rate for occupancy sensors.
Getting a 2nd hand seat to match, or a damaged 2nd hand seat and remove the sensor pad.
Or
Buy a set of more modern 720s/570s etc seats as by all accounts they are more comfortable, Thorney did a video on the swap
I remember reading something about this on Mclarenlife which covered the issue with the older seats.
You won't be able to use a resistor, apparently Mclarens have variable rate for occupancy sensors.
Me too !.
2012 12c Coupe - Airbag light on due to "Left front seat occupancy sensor failure" (ORC B1BAB00 code).
Mc Ascot quoted for the "upgrade" mat kit today - £2600 parts, 5h labour & main stealer electroncs re config ..... and parts are "on back order with no ETA" (!!!).
I've been trying to source a new sensor all day - got nowhere
Next roll of the dice, I've taken the part off and removed the cover for the electronics on it. There's a surface mount Zener Diode on the board that I suspect may be the failure mode. I've identified it and bought 10 off ebay for .....
wait for it .......
99p (yes, in total, for 10)
when they arrive next week I'll solder one on.
If it works It's got to be some sort of record for quoted price (circa £4k) to cost of DIY repair (9.9p). I'm finding it hard to think I might be that lucky, gotta try to find out I suppose.
Watch this space.
2012 12c Coupe - Airbag light on due to "Left front seat occupancy sensor failure" (ORC B1BAB00 code).
Mc Ascot quoted for the "upgrade" mat kit today - £2600 parts, 5h labour & main stealer electroncs re config ..... and parts are "on back order with no ETA" (!!!).
I've been trying to source a new sensor all day - got nowhere
Next roll of the dice, I've taken the part off and removed the cover for the electronics on it. There's a surface mount Zener Diode on the board that I suspect may be the failure mode. I've identified it and bought 10 off ebay for .....
wait for it .......
99p (yes, in total, for 10)
when they arrive next week I'll solder one on.
If it works It's got to be some sort of record for quoted price (circa £4k) to cost of DIY repair (9.9p). I'm finding it hard to think I might be that lucky, gotta try to find out I suppose.
Watch this space.
Edited by speedick on Thursday 29th January 22:09
A few more thoughts
The sensors are actually tourqe measuring devices. There's a flat on the shaft under the Torx nut that locks to the seat rail and the lever that raises / lowers the seat height scissors the sensor shaft so that It can measure the applied rotational force and output via a transducer (which increases when there's someone sat on the seat obviously.)
The part is branded "BAG" and theres a long Alphanumeric part number on it .... I can't figure out who originally made it though (Although I suspect that the Airbag ECU is by either Bosch or Siemens)
Output is by 4 pin plug. I'm suspecting a reference voltage (the Zener Diode is rated at 27v), ground and 2 signal pins - So probably canbus. Also, the 4 sensors are location specific - I can see why left & right would be different (due to reversed rotational torque) but front and rear differences probably indicate different calibrations and therefore dedicated canbus identification to the car's ecu. I dont think a simple resistor "cheat box" is going to solve this.
If anybody can offer any more clues they would be greatly appreciated.
The sensors are actually tourqe measuring devices. There's a flat on the shaft under the Torx nut that locks to the seat rail and the lever that raises / lowers the seat height scissors the sensor shaft so that It can measure the applied rotational force and output via a transducer (which increases when there's someone sat on the seat obviously.)
The part is branded "BAG" and theres a long Alphanumeric part number on it .... I can't figure out who originally made it though (Although I suspect that the Airbag ECU is by either Bosch or Siemens)
Output is by 4 pin plug. I'm suspecting a reference voltage (the Zener Diode is rated at 27v), ground and 2 signal pins - So probably canbus. Also, the 4 sensors are location specific - I can see why left & right would be different (due to reversed rotational torque) but front and rear differences probably indicate different calibrations and therefore dedicated canbus identification to the car's ecu. I dont think a simple resistor "cheat box" is going to solve this.
If anybody can offer any more clues they would be greatly appreciated.
Edited by speedick on Thursday 29th January 22:23
Edited by speedick on Thursday 29th January 22:24
Update.
I removed and dismantled the sensor (Left / Front one was being reported as the fault). It's fairly easy to get the plastic cap off the top of the PCB housing / loom connector (dremel the top of 2 plastic pins holding it.)
Inside there's a flexible PCB with 3 surface mounted components on it and 4 soldered connections to the main part of the sensor underneath.
My suspected failed component was a sufrace mount Zener diode P27 (3 pin, 27 Volt "S-23" style from memory). They are easy enough to obtain - but TINY (about 1.5 x .75 mm rectangle)
I removed the old component with desoldering braid fairly easily. Fitting a new one is VERY difficult, mainly due to the PCB being a flexible plastic that melts at under soldering temp (350c). Also, I think the tracks are possibly conductive ink not copper plate. Anyway, I eventually managed to get a new part on with electrically sound (but not pretty) connections.
The seat was re assembled, ECU plugged in and airbag fault removed no problem (we could not do this before the component replacement). Car started and shut down several times without it coming back - feeling pretty smug at this point.
A celebratory Tea and set off to drive home, about 10 miles in and ..... The airbag light comes back on (!!!).
Oh well, it was nice while it lasted.
On reflection my best guess is now that a fault of some sort in the sensor took out the Zener Diode. The replacement did seem to work, but I'm guessing that whatever caused the 1st one to fail also did for my replacement. The body of the sensor is Stainless steel & Lazer welded - I'd have to admit it's probably DIY proof.
I've written this up in case anyone else comes along to this thread in the future - If so, good luck (and please do share if you find a fix that works). I'm off to plan B (use the Mc Conversion kit) but may have to wait for the Mc parts.
I removed and dismantled the sensor (Left / Front one was being reported as the fault). It's fairly easy to get the plastic cap off the top of the PCB housing / loom connector (dremel the top of 2 plastic pins holding it.)
Inside there's a flexible PCB with 3 surface mounted components on it and 4 soldered connections to the main part of the sensor underneath.
My suspected failed component was a sufrace mount Zener diode P27 (3 pin, 27 Volt "S-23" style from memory). They are easy enough to obtain - but TINY (about 1.5 x .75 mm rectangle)
I removed the old component with desoldering braid fairly easily. Fitting a new one is VERY difficult, mainly due to the PCB being a flexible plastic that melts at under soldering temp (350c). Also, I think the tracks are possibly conductive ink not copper plate. Anyway, I eventually managed to get a new part on with electrically sound (but not pretty) connections.
The seat was re assembled, ECU plugged in and airbag fault removed no problem (we could not do this before the component replacement). Car started and shut down several times without it coming back - feeling pretty smug at this point.
A celebratory Tea and set off to drive home, about 10 miles in and ..... The airbag light comes back on (!!!).
Oh well, it was nice while it lasted.
On reflection my best guess is now that a fault of some sort in the sensor took out the Zener Diode. The replacement did seem to work, but I'm guessing that whatever caused the 1st one to fail also did for my replacement. The body of the sensor is Stainless steel & Lazer welded - I'd have to admit it's probably DIY proof.
I've written this up in case anyone else comes along to this thread in the future - If so, good luck (and please do share if you find a fix that works). I'm off to plan B (use the Mc Conversion kit) but may have to wait for the Mc parts.
Edited by speedick on Thursday 5th February 08:03
Edited by speedick on Thursday 5th February 08:04
I'd spotted the apex one.
Unfortunately theres much more to it, the Mc "upgrade" kit comprises Mat, Heater Pad, Steel bracket, 2 ECU's a seat wiring loom and a different plastic seat pan.
Its a 5 hour fit and needs main dealer software alterations to configure (I have the Mc Workshop instructions to do this if anyone needs them).
I suppose it makes the cost seem a tiny bit more reasonable .... BUT this is a design flaw that resulted in 100 % of the cars sold in the USA having a retro fit under a free recall program.
Mc HQ "I know, lets call it an upgrade and make the customers pay £4500 for it here in the uk" ?
I went and bought a pair of the later ('13 onward) seats complete this morning. They have all the "upgrade" spec bits as standard (but will still need to be coded to the car).
I'm philososhical, Bought my 12c 8 years ago, I've done 14000 miles in it (enjoyably) and virtually nothing has ever gone wrong with it (wiper motor and a side reflector, thats it). This looks set to cost about £2500 to fix, I'm trying to see it as an average of £350 / year during my ownership.
Unfortunately theres much more to it, the Mc "upgrade" kit comprises Mat, Heater Pad, Steel bracket, 2 ECU's a seat wiring loom and a different plastic seat pan.
Its a 5 hour fit and needs main dealer software alterations to configure (I have the Mc Workshop instructions to do this if anyone needs them).
I suppose it makes the cost seem a tiny bit more reasonable .... BUT this is a design flaw that resulted in 100 % of the cars sold in the USA having a retro fit under a free recall program.
Mc HQ "I know, lets call it an upgrade and make the customers pay £4500 for it here in the uk" ?
I went and bought a pair of the later ('13 onward) seats complete this morning. They have all the "upgrade" spec bits as standard (but will still need to be coded to the car).
I'm philososhical, Bought my 12c 8 years ago, I've done 14000 miles in it (enjoyably) and virtually nothing has ever gone wrong with it (wiper motor and a side reflector, thats it). This looks set to cost about £2500 to fix, I'm trying to see it as an average of £350 / year during my ownership.
Edited by speedick on Thursday 5th February 13:42
speedick said:
Update.
I removed and dismantled the sensor (Left / Front one was being reported as the fault). It's fairly easy to get the plastic cap off the top of the PCB housing / loom connector (dremel the top of 2 plastic pins holding it.)
Inside there's a flexible PCB with 3 surface mounted components on it and 4 soldered connections to the main part of the sensor underneath.
My suspected failed component was a sufrace mount Zener diode P27 (3 pin, 27 Volt "S-23" style from memory). They are easy enough to obtain - but TINY (about 1.5 x .75 mm rectangle)
I removed the old component with desoldering braid fairly easily. Fitting a new one is VERY difficult, mainly due to the PCB being a flexible plastic that melts at under soldering temp (350c). Also, I think the tracks are possibly conductive ink not copper plate. Anyway, I eventually managed to get a new part on with electrically sound (but not pretty) connections.
The seat was re assembled, ECU plugged in and airbag fault removed no problem (we could not do this before the component replacement). Car started and shut down several times without it coming back - feeling pretty smug at this point.
A celebratory Tea and set off to drive home, about 10 miles in and ..... The airbag light comes back on (!!!).
Oh well, it was nice while it lasted.
On reflection my best guess is now that a fault of some sort in the sensor took out the Zener Diode. The replacement did seem to work, but I'm guessing that whatever caused the 1st one to fail also did for my replacement. The body of the sensor is Stainless steel & Lazer welded - I'd have to admit it's probably DIY proof.
I've written this up in case anyone else comes along to this thread in the future - If so, good luck (and please do share if you find a fix that works). I'm off to plan B (use the Mc Conversion kit) but may have to wait for the Mc parts.
Good try, you obviously know your way around semi-conductors.I removed and dismantled the sensor (Left / Front one was being reported as the fault). It's fairly easy to get the plastic cap off the top of the PCB housing / loom connector (dremel the top of 2 plastic pins holding it.)
Inside there's a flexible PCB with 3 surface mounted components on it and 4 soldered connections to the main part of the sensor underneath.
My suspected failed component was a sufrace mount Zener diode P27 (3 pin, 27 Volt "S-23" style from memory). They are easy enough to obtain - but TINY (about 1.5 x .75 mm rectangle)
I removed the old component with desoldering braid fairly easily. Fitting a new one is VERY difficult, mainly due to the PCB being a flexible plastic that melts at under soldering temp (350c). Also, I think the tracks are possibly conductive ink not copper plate. Anyway, I eventually managed to get a new part on with electrically sound (but not pretty) connections.
The seat was re assembled, ECU plugged in and airbag fault removed no problem (we could not do this before the component replacement). Car started and shut down several times without it coming back - feeling pretty smug at this point.
A celebratory Tea and set off to drive home, about 10 miles in and ..... The airbag light comes back on (!!!).
Oh well, it was nice while it lasted.
On reflection my best guess is now that a fault of some sort in the sensor took out the Zener Diode. The replacement did seem to work, but I'm guessing that whatever caused the 1st one to fail also did for my replacement. The body of the sensor is Stainless steel & Lazer welded - I'd have to admit it's probably DIY proof.
I've written this up in case anyone else comes along to this thread in the future - If so, good luck (and please do share if you find a fix that works). I'm off to plan B (use the Mc Conversion kit) but may have to wait for the Mc parts.
Edited by speedick on Thursday 5th February 08:03
Edited by speedick on Thursday 5th February 08:04
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