Discovery 4 SEAT BASE fix!!

[andeck]

Hi all,


I thought I'd share what I did with my D4 yesterday in the hopes that many seat bases will have a long and good looking life. Doing this will probably result in some faults that you can see with a fancy Nanocom or some such, but nothing you can see day to day.


Two caveats:
1. I'm not responsible for your car, I'm just sharing what I found out.
2. This is NOT FOR NORTH AMERICAN MARKET CARS! The NAS market has a different occupant detection system, so may affect how the airbags deploy.


I bought my car 2011 D4 SDV6 HSE () with a previous repair on the seat cushion side bolster. I think this is the usual wear every car will see over time, as everyone slides in and out over it. My cushion was collapsed and the repair was starting to crack again as you will see in the photo.


Well, the trick is to swap it with the passenger seat base while it still looks in decent nick. This will double the life of your seat bases, because after searching on and off for a few weeks it looks like they are hard to come by on their own.


You will need:

• 
  
  • a T40 bit and ratchet
  • a screwdriver or other levering device.
  • A zip tie or two.
  • An hour or less

Drivers seat:

1. Raise seat base to full height
2. Undo the 4 torx bolts (refer pictures)
3. Unclip the wires running though the clips at the back (refer pictures).
4. Lift the base up to get access, and lever out the plastic fastener holding the wire (refer pictures).
5. Unplug the wide green plug (heating), noting the way the wire is routed around rails.

Passengers seat is the same as driver, except it has two wiring plugs to remove. One is for the heating (same wide green plug), and the other is the switch that activates that annoying bong when the passenger hasn't put their belt on, or you have something heavy on the seat. This is two wires wrapped in white, going to a different module (also green plug).


The drivers seat base doesn't need this, as bigger problems are at hand if the car is moving and no one is in the drivers seat!




Once they are out, you will notice the wires are routed to the centerline side of the seat bases, so you will need to lever these fasteners out and put them in the holes on the new centerline side. Don't cut them, you should be able to just swap them. With the smaller green plug, I just zip tied to the seat base out of the way, as you won't be plugging this in anywhere.


Installation is the reverse, routing the wires where they went before, and plugging in the green plug. You might also give it a quick vacuum while your at it.

I found a dollar and 10 cents!!! WOOHOOO!!


The torque on the bolts is 25Nm if your interested, but I just nipped mine nice and snug.


Once installed, you will want to check that it still works. You have to start the car to run the front seat heating. I tried without and thought I'd wasted my time, but once started they switched as usual.
Another plus is the bong is gone!!






I checked out the wiring diagrams I have, and I conclude that the airbag system will not be disabled, except perhaps in the NAS market (thus the caveat).The second plug in the NAS market will also have 3 wires in it, not just two.



Excerpts regarding this issue (bold and red text pertinent):


OCCUPANT SENSING


There are two types of occupant sensing:
In all markets except North America, vehicles have an occupant detection system to activate the seat belt minder
On NAS vehicles, an occupant classification system provides signals to the RCM to allow the correct arming of the passenger air bag and corresponding indicator.


The instrument cluster supplies a reference voltage to the pressure switch and measures the current draw to determine the occupancy status. From the occupancy status, and the status of the front passenger safety belt (received from the RCM on the high speed CAN bus), the instrument cluster determines the belt minder status.


SRS OPERATION
General


In a collision, the sudden deceleration or acceleration is measured by the safing sensor in the RCM and by the impact sensors. The RCM evaluates the readings to determine the impact point on the vehicle and whether the deceleration/acceleration readings exceed the limits for firing any of the air bags or pretensioners. During a collision, the RCM only fires the air bags and pretensioners if the safing sensor confirms that the data from the remote sensor(s) indicates an impact limit has been exceeded. The RCM also monitors the vehicle for a roll-over accident using the internal roll-over sensor and high speed CAN (controller area network) bus messages from the anti-lock brake system (ABS) module and the steering angle sensor.


The RCM incorporates the following impact thresholds to cater for different accident scenarios:
Front impact, pretensioners.
Front impact, driver and passenger air bags stage 1, belt unfastened.
Front impact, driver and passenger air bags stage 2, belt unfastened.
Front impact, driver and passenger air bags stage 1, belt fastened.
Front impact, driver and passenger air bags stage 2, belt fastened.
Rear impact.
LH (left-hand) side impact.
RH (right-hand) side impact.
Roll-over.
The front impact thresholds increase in severity from pretensioners, through to driver and passenger air bag stage 2, belt fastened.




Firing Strategies


The seat belt pretensioners are fired when either the pretensioner impact limit or the roll-over limit is exceeded. The RCM only fires the pretensioners if the related safety belt is fastened.For the front passenger pretensioner to fire, the seat must also be occupied by a large person, i.e. someone over a given weight (NAS only).
The driver and passenger air bags are only fired in a frontal impact that exceeds the stage 1 threshold. Both stages of the inflator in the driver and passenger air bags are fired. At impacts between the stage 1 and 2 thresholds, the delay between the firing of the two stages varies with the severity of the impact; the more severe the impact the shorter the delay.


At stage 2 impact thresholds and above, the two stages of the inflator are fired almost simultaneously. The passenger air bag is disabled unless the front passenger seat is occupied by a large person (NAS only), or the passenger air bag deactivation switch is on (all except NAS).The time delay between firing the two stages of the inflator in the driver air bag is increased if the driver seat is forward of the seat position sensor switching point. If there is a fault with a safety belt buckle sensor, the RCM assumes the related safety belt is fastened for the pretensioner firing strategy and unfastened for the driver and passenger air bag firing strategies. If there is a fault with the occupant detection system, or if there is a fault with the passenger air bag deactivation switch, the RCMincrease the time delaybetween firing the two stages of the inflator in the passenger air bag.


Regarding this increase in time delay, I think it will be trumped by the 'belt fastened' scenario.



The seat now looks and feels great and should last for another few years at least. Catch yours before it needs a repair. I take no responsibility for your car but have provided information needed if you choose to do this. Hope it helps many people.