How to Install B6 S4 Recaro Seats into a B7 A4 with No Airbag Warning Light

I recently acquired a set of beautiful platinum grey Recaro seats out of a B6 (2001.5-2005.5) Audi S4. While these Recaros easily bolted up to the stock mounting locations in the floor and the wiring plugged right into the B7 wiring harnesses, an airbag warning light appeared on my dash after installing my Recaros and driving home. The airbag warning light occurs because B6 A4 & S4s do not have a pressure control module in the front passenger seat (this part is often referred to as pressure plate, or even a bladder, although it is really a hydraulic system). This module is essential to the functionality of the B7 Airbag system, as it determines if someone is sitting in the passenger seat and will activate/deactivate the airbag system for the passenger side accordingly. If this sensor isn’t found, a warning light is triggered which disables all airbags in the car – not good.

To fix this, you’ll need to swap the pressure control module from your original B7 A4 seats into the B6 seats. You must also swap the seat buckle from your B7 seats, since the pressure control module plugs into the seat belt buckle and the airbag system checks for both a seat belt & the pressure control module to enable the passenger airbag.

If you have Recaro seats from a B7 Audi S4 or RS4, the install is plug and play as these seats already have the pressure control module – simply follow step 1 below to remove your A4 seats, and do the reverse of Step 1 to install your new seats. If however you bought (or are interesting in buying) a set of Recaro seats from a B6 Audi S4, the process requires a few more steps, which I’ll cover in detail below. This DIY will cover the entire process, including seat removal and install if you’ve never done it before (super easy!)

• Skill Level (1/10, 10 the hardest): About a 5 if you are patient
• Time Required: 3-5 hours depending on skill level & familiarity
• Tools Required: Triple Square (or T-50 Torx bit and Channel Locks if you don’t have one), Socket Wrench, Wire Cutters, Wire Connectors or Soldering Iron, Electrical Tape, VAG-COM cable or access to one, flat head & Phillips screwdrivers, loads of patience

I strongly recommend reading this DIY all the way through before starting so you fully understand what is involved and why everything needs to be done and how it all works! Also, I recommend not cutting any corners when doing this – the system is VERY sensitive. If the wiring has any kinks in it, the pressure control module isn’t secured and lying flat in the factory location, or anything else is even slightly off, you’ll still have an airbag light out. It took me several attempts before I finally got the airbag light to go away because I cut corners and did not mount the ballasts & pressure control plate securely and left the old wiring in too – cutting corners does NOT save you time with this mod…be thorough and meticulous!

Step 1: Remove your B7 A4 Seats

Removing your seats is quite simple. There are four bolts that hold it in place along the sliding rails on the bottom of the seat. Two are in front, and two are behind the seat. Move the seat all the way forward to get to the back ones, and all the way back to get to the front ones. Use a  triple square to remove the four bolts holding the seat in. If you don’t have a triple square,  a T50 Torx Bit and a socket wrench will work too if you don’t have a triple square – just be careful not to strip the bolts (some stripping is probably inevitable, so just be careful). Remove the bolts all of the way and then raise the seat as high as it will go, center the seat in the middle of the tracks, and adjust the incline of the seat so that it is fully upright or even slightly inclined making an acute angle – this will make it easier to get in and out of the doorway as well as easier to work on once out of the car.

Once the seat is totally unbolted, tilt it back and disconnect the wiring harnesses. There are three or four plugs to pull out, depending on if you have heated seats or not. Be careful and do not tug the wires directly as you don’t want to pull anything out of the harness.

Lastly, you’ll have to detach the base of the seatbelt from its anchor point on the seat itself. Remove the plastic cover and you’ll see the seat the seat belt ends in a metal fixture which snaps over a bolt – it’s actually a simple mechanism. To remove it, simply pull the tab outward and push the metal clip downward and it will slide off the circular bolt. The picture below should help illustrate what it looks like:

Step 2: Removing the Seat Belt Buckle from your B7 A4 Seats

Now that we have the seat out of the car, it’s time to start disassembling it. Start with removing the seat belt buckle, as the more stuff you get out of the way, the easier it is to get the pressure plate out later. To remove the seat belt buckle, use a triple square to loosen the bolt. If you don’t have a triple square, use a set of Channel locks to loosen the bolt – this will put some small dents or bite marks into the bolt (see below), but the bolt is hidden from view once installed anyway. Once the bolt is out, also unplug the wiring harness (which plugs into the pressure control module and will be critical for later) and you can completely remove the seat belt buckle.

So far, so easy! Now on to the fun stuff!

Step 3: Removing the B7 Pressure Control Module (Pressure Plate)

This is scarier than it sounds, but you’ll be partially taking apart the bottom of your seat to get this out. Once complete, no one will be able to tell you ever touched your seats yet alone took them apart. Start by removing the storage compartment under the seat, as it really clears up a lot of room and you’ll be thankful later. It is held on by four T25 screws. If you don’t have torx bits, a set of hex keys or allen keys should do the trick. Their mounting locations are as shown:

Now that you have that out of the way, time to (partially) remove the seat cover off of the bottom of the seat. Start with removing the two metal clips on the bottom of the seat:

Next, you’ll see that the fabric is stretched on all four sides of the seats – you only need to remove the front edge and one of the side edges to have enough room to pull out the pressure plate. Leaving the back and other side edge attached will help you put the seat back together and save a lot of time, although you can take off more if you really want (I took off three edges before realizing I probably only needed to take off two). At the end of the fabric it is capped off with a rubber fitting that runs the length of the bottom of the seat along all four edges. That rubber fitting stretches over black metal prongs on the bottom of the seat, which holds the fabric securely over the seat cushion. To remove the fabric, you’ll have to pull the rubber fitting off of the metal prongs one by one, and it will simply come loose. This is easier to explain by a picture – I pried it off using a flat head screwdriver, although some popped off just using my hands:

After prying it off, you can see the black metal prongs that the rubber fitting at the end of the seat fabric hooks onto:

The front comes off by either snapping the rubber fitting off the black metal prongs (like above for the side edge) or by removing three torx screws that you can see when you remove the storage compartment. You should now be able to peel back the entire front edge, and at least one side edge – remove the side that doesn’t have the panel to adjust the seats, it’s much less complicated…

Once you have the front and side edges removed, you can pull the cushion and fabric far enough back to expose the Pressure Control module:

Removing the pressure control plate is pretty easy, there are three black tabs you need to pop out (two pictured above, and a third one near the back of the pressure control module), you can remove these by pushing them through from the underside of the seat. To remove the red plastic anchor into the seat cushion foam  you can either rip it out, as I did, or be gentle about it and try to get it out otherwise – you won’t really be able to reuse that mounting point regardless. When removing the pressure plate, all you need to pull through is the hydraulic hose and the plug/sensor at the end of it.  That sensor has a connector that connects to the wiring harness which has a ‘do not disconnect’ sticker on it.  Go ahead and disconnect that and just pull the plate through with that hose and connector only (note: do this at your own risk. If you want to be absolutely cautious, pull all of the wiring through in tact, however you can disconnect this cable without any permanent problems or issues).  From here, you can re-assemble the top portion of the donor B7 seat and now focus on removing the wiring from beneath your B7 seat.

An important point to remember is that the plate system is hydraulic, and filled with fluid. If you try to cut or disconnect the hose or sensor, you can permanently damage the plate/system and it may not work again. Only disconnect at the point where the factory harnesses plug in to each other!

Next, you’ll want to remove the rest of the wiring for the pressure plate – from the harness you disconnected from the pressure control module’s hose, all the way down to the black harness that plugs into the ground of the car. To do this, you  should unwind all the fabric tape to gain access to the wiring, although another option is slicing through the tape to ‘split’ it open.  This is much more dangerous, as you run the risk of cutting the sheath.  Once the wiring is free, it can be separated from the rest of the wiring pretty easily.  You will also need to unscrew the control module/ballast for the pressure control plate wiring, and the two harness connector mounts can pop out as well.

A word to the wise: It is critical it is to pay close attention to the wiring on both the donor seat and transplant seat. This way you can mimic the same mounting points and route the wires the exact same way. Make mental notes (or take pictures) so you can trace every wire and where they are mounted on the bottom of the seat, what holes or passages they go through, etc. The system is VERY sensitive, so installing it as close to factory spec as possible will ensure minimal issues and allow the system to work as it should.

Step 4: Preparing the B6 Recaro

First, start by removing the old seat belt buckle and the old airbag wiring harness.

Next, remove the storage compartment for easier access to remove the old wiring and install the new wiring. It’s the same process as before, there are four bolts that can be removed using hex keys or a torx bit and then the storage compartment will come off.

Once the storage compartment is off, you can then remove all of the old wiring very easily. You’ll want to take out the wiring for the old black plug that went from the seat belt buckle to the black harness on the floor of your car. It is not necessary and best to get it out of the way to avoid any mistakes or problems down the road.

And now, we’re ready for the pressure control module transplant surgery. Take a deep breath, it’s time to take apart those lovely Recaro seats you paid a pretty penny for.

Step 5: Installing the Pressure Control Module in the B6 Recaro Seat

The leather Recaro fabric removes the same way as before – disconnect the rubber fitting at the end of the fabric from the metal prongs on the underside of the seat. You really only need to remove one side of the seat, and the front edge of the seat – you can leave the back edge and one of the side edges still firmly attached.

The side edge removes the same as before, use a flat head screw driver to pull the rubber fitting off of the metal prongs. The front edge can be removed by removing 3 torx screws behind where the storage compartment used to be. If you can’t get to those, it will pop out of place if you pull on it, although you may weaken the clips or tear the fabric if you’re not super careful.

I only needed to remove the front and side to have enough room to squeeze my hands under the seat cushion to feed the wiring through the hole in the seat and place the pressure plate in, and attach it to the mounting points on the bottom of the seat. There are three mounting points, two toward the front of the seat, and one in the middle toward the back of the pressure plate.  MAKE SURE IT IS SECURED AT ALL THREE POINTS! The pressure plate is VERY sensitive, and you need to make sure it is lying securely in place and will not move around!

You will also need to cut a small 1″ slit in the white cloth to pass the wiring and hose through it. Be sure to place the pressure control module ON TOP of the cloth, so the cloth will protect the pressure control module from getting snagged on the metal base of the seat. Since the pressure control module is hydraulic, a snag in the plastic could cause the liquid to leak, which would then ruin the system.

Woohoo! The hard part is done. Now let’s put your seat back together so it looks normal again. Once you’ve made sure the pressure control module is secured and lying flat without pinching any wiring or anything, simply reattach the edge of the seat to the black metal prongs, and snap back in the front of the seat…and voila, no one could probably ever tell you did anything to the seat!

Step 6: Wiring & Installing the Recaro Seat

It’s pretty simple from here. The new pressure control module plugs into two places: the seat belt buckle and the harness on the floor of your car. If you haven’t already, install the b7 seat belt buckle, and the smaller harness of the pressure control module will plug in to the wiring coming off of the seat belt buckle.

Next, clean up the wiring with electrical tape and secure the pressure control module wiring by taping it to the other wiring going into the ground (the green, red, and yellow harnesses). I have created a diagram on where I mounted everything on my seat – however, your seat could be different, and I may have parts of this wrong. If you wired it differently please contact me and send me a picture, I’d love see other options as I didn’t take very good notes and had to kind of guess where everything was supposed to go. Either way, you’ll want to make sure to follow factory wiring and mounting locations as close as possible, and make sure the hose coming out of the pressure control module isn’t pinched or bent, as this will make it impossible to recalibrate the system.

Also, the brown harness clips in to a factory spot too:

Once everything is prepped, taped, mounted and secured, it’s time to put the seat back into the car. Angle the seat into the car headrest first until you’ve got the entire seat inside of the cabin, and then tilt the seat backward so you can access the wiring under the seat and plug it into the harnesses on the floor

The harnesses on the floor appear as below:

The black plug is where the pressure control module will plug into

The green plug is for heated seats

The red plug is for powering the seat (reclining, lumbar, etc)

The yellow plug is for the seat’s airbag

The green, red, and yellow plugs should all be the original B6 Recaro wiring – you shouldn’t have touched nor altered those in anyway. The only wiring that is different now is the harness that will plug into the black plug on the floor!

The black harness coming from the B7 pressure plate will look somewhat like this:

You’ll notice that there are three active posts on one side of the harness, and only two on the other side. You’ll want to make sure that the side with three active posts (the copper looking contact points) plugs into the harness on the floor along the side nearest the middle of your car, and the side with only two active posts plugs into the side facing the door jam. I did this incorrectly the first few times and got faulty wiring errors when reading the codes in VAG-COM.

Once you’ve plugged it all in, it should look like this (only prettier, as I used a ton of electrical tape, haha)

Before you go and bolt the seat back into place, let’s test everything and re-code the seats (if necessary) to make sure there aren’t any more changes that are needed. Personally, I had the plug in the wrong way, so I had to try it both ways before it finally worked

Step 7: Checking Fault Codes & Applying the Basic Setting to calibrate the Pressure Control Module

It is possible you wont need to clear any fault codes and the airbag light will have gone away by now, if you used the same pressure control plate that was previously installed in you car and the car was never turned on with the seat removed. If the car was turned on with the seat removed from the car, the airbag light will stay until it’s cleared through VAG-COM. Additionally, if the pressure control module came out of a different car, you will also need to clear the fault codes in VAG-COM and also re-calibrate it (apply the basic setting) before your car can recognize and use it.

With everything plugged in, insert your Ross-Tech VAG-COM cable into your car and fire up the VCDS software. I do not know if hacked “eBay” VAG-COM cables will work for programming the airbag module, but I highly recommend using authentic Ross-Tech cables regardless – this is not a corner you want to cut, and the $349 purchase price of this cable is well worth it in the long run. A big thank you and a strong recommendation for Ross-Tech.

Once you have VCDS open, go to Application 15 – Airbags. Check the fault codes – you’ll probably have a bunch of them. If one of them reads “01044 – Control Module Incorrectly Coded” be sure to go into your coding and reset the coding first. My airbag coding is set to: 0032607 which should be the same for pretty much any North America B7 Audi A4 WITHOUT rear side airbags.  For a full set of coding instructions and what they mean, visit the Ross-Tech Wiki.

Regardless, you’ll want to clear all of your codes before proceeding. If the airbag warning light goes away after you cleared your fault codes, great you can go ahead and bolt your seat back in place and you’re done!

If not, we’ll need to apply the basic setting to it recalibrate it.

To apply the basic setting, follow these instructions:

Basic Setting

Seat Occupied Recognition Control Module (J706)If the Seat Occupied Recognition Control Module (J706) or the seat itself have been replaced, the basic setting has to be performed.

[Select]
[15 – Airbags]
[Security Access – 16]
Enter 30475, to enable the basic setting.
If you are having problems performing this security access, contact us.
[Do it!]
[Basic Settings – 04]
Group 001
[Go!]
Activate the Basic Setting.
[ON/OFF/Next]
The reset has been performed.
[Done, Go Back]
[Close Controller, Go Back – 06]

After applying the basic setting, go ahead and clear your codes one last time. The airbag light should now be gone permanently! At this point, pat yourself on the back and go on a nice long road trip to enjoy your super comfortable Recaro seats! You’ve done it!

To be extra sure everything is working properly, sit in the passenger seat with the car running and buckle your seatbelt. The central display should now say “PASSENGER AIRBAG ON”

Step 8 – Power Seat Fuse

If you didn’t have power seats on the passenger side before, then you need to increase the size of the fuse for the passenger door (the driver’s door is always power, I believe). If you don’t increase the fuse size, it will probably blow the fuse after adjusting it once or twice. The good news is that it’s very easy to replace the fuse – just pull back the passenger kick panel (you don’t need to remove any bolts/screws) and you can reach it. Replace the 10A fuse for non-power seats and replace with a 30A fuse for power seats.

Troubleshooting:

If you’ve followed these steps to a T and are still having problems, here are my suggestions on problem areas to troubleshoot:

• The black wiring harness that plugs into the floor: Try plugging it in the other way, experimenting with which side the three active contact points are on (facing the middle of the car or facing the door jam). It can physically be plugged in either way without problems, so this is easy to connect incorrectly. After plugging it in a different way, go through Step 7 (Coding & Recalibrating) again.
• Follow all of the wiring to make sure there are no shorts or bad connections – it is likely that you may have had to cut a few wires to remove the wiring from the b7 seat if the wiring was really tangled – I know I did. If you cut any wires and re-attached them, double check all of those connections!
• Check your coding – make sure that you aren’t getting a fault code for Incorrectly Coded and set everything back to factory
• Make sure the pressure plate isn’t getting pinched anywhere, or that the wiring coming out of the pressure plate isn’t bent or getting pulled on before going through the bottom of the seat
• If the passenger airbag is always on, even when someone isn’t sitting in it, it could be that the pressure control module isn’t lying flat, or the hydraulic hose coming out of it leading into the ballast is pinched. If the plate or its wiring is getting pinched or has too much pressure applied to it, you can’t calibrate it properly and the system won’t work right. To fix this check the pressure control plate is mounted securely and flat and make sure the wiring coming out of the plate is not getting pinched or caught on anything.
• Make sure you’ve removed all of the old wiring you’re not using and that all of the pressure control module wiring is mounted to the bottom of the seat securely at the factory mounting points.

Disclaimer: Any information in this post is purely for entertainment purposes only and I am no way liable for any damage you may incur to your car or your body. Any modifications are performed at your own risk. Obviously, the airbag system is a critical component to your car’s safety and can be quite costly to replace, please take the utmost care when altering anything to do with the airbag wiring system.