My back has been killing me since I've gotten my 25 GX in August. The lumbar will deflate within 3-4 hours on both the driver's and passenger's side, and after my dealer told me it was "expected behavior", I took matters into my own hands. Here's what you can do to solve this problem yourself if you have the same issue.
Note: This DIY only applies to Luxury, Luxury+, and Overtrail+ seats with massaging functionality (though I haven't yet heard of a non-massaging seat with leaky lumbar).
REMOVING THE SEATBACK
THE PROBLEM
The reason your lumbar deflates is because the lumbar hose is hooked to the air system via a connection that doesn't have barbs, and it doesn't come from the factory with a clamp. The lumbar is just supposed to magically stay inflated using a hose that's held on by hopes and dreams. I fully believe every GX550 with this design will have leaky lumbar within the next 1-2 years - and I cannot believe Lexus thought this was good enough to send out the door.
Here's a picture of my passenger seat. This yellow hose I'm pointing to is the hose which inflates the lumbar bladder. You can also see that my 2025 already has the hose clamp described in TSB L-SB-0042-24 for 2024s which have non-functioning massage seats (grey / clear hose)
THE FIX
I bought a pack of 6 more of those hose clamps you can see on the grey / clear hose, and I'm gonna clamp each of the 3 non-barbed fittings I can see. Lexus part number 90466-06001 - Bell Lexus Parts has them online for less than $2 each with free shipping. Unfortunately, this appears to be a Lexus-only part number, so you're gonna have to get it directly from Lexus, though I'm sure a zip tie or other clamps would work the same. I believe you could get away with just clamping the yellow line, but the parts were so cheap I decided to clamp them all.
Simply use your fingers (ONLY - no tools) to unplug the hose, slip the hose clamp onto the hose, reattach it, and move the clamp into place.
Warning: Some of these hoses are very close together. Make sure to position the metal clamp somewhere it isn't touching any hoses, or else the clamp will rub through the hose and you'll get air leaks that way. Triple check to make sure your clamps aren't touching any hoses or wires. I chose not to clamp the clear / grey hose on my passenger side seat (to the left of my finger above) because another hose is routed and touching right where the clamp has to go. Luckily, that appears to be the purge line and it's never under any pressure.
Here's a picture of the back of my passenger seat with 2 out of 3 clamps attached, because I was worried about chafing:
THAT'S IT!
Reinstallation of the seat back is the reverse of removal. Align the seatback, push the top hangers back up into place, reinstall the screws (pro tip - push the seatback upward while screwing it in for less panel gap between the seat and the seatback), and re-hook the elastic.
You did it! Your lumbar should now not deflate at all, and it should also feel significantly stiffer. Now let's go call Lexus to tell them they should have done this at the factory.
Note: This DIY only applies to Luxury, Luxury+, and Overtrail+ seats with massaging functionality (though I haven't yet heard of a non-massaging seat with leaky lumbar).
REMOVING THE SEATBACK
- (optional, for convenience & room) Move the seat into the forward-most position, the highest seat cushion position, and with the seatback folded forward as much as possible
- Reach underneath the seat and feel for an elastic band which secures the felt section of the bottom of the seatback to the underside of the seat
- Unhook the elastic band from the clips - there's two hooks under the seat. Here's what the felt section & elastic band look like once unhooked:
- Unscrew the two screws under the felt flap. I used a JIS screwdriver, but I'm not sure if it's necessary. Here's a pic of those screws:
- Remove the seatback by pulling it down. If it's stuck, push the top of the seatback into the seat and pull down. They're kind of on hangers.
THE PROBLEM
The reason your lumbar deflates is because the lumbar hose is hooked to the air system via a connection that doesn't have barbs, and it doesn't come from the factory with a clamp. The lumbar is just supposed to magically stay inflated using a hose that's held on by hopes and dreams. I fully believe every GX550 with this design will have leaky lumbar within the next 1-2 years - and I cannot believe Lexus thought this was good enough to send out the door.
Here's a picture of my passenger seat. This yellow hose I'm pointing to is the hose which inflates the lumbar bladder. You can also see that my 2025 already has the hose clamp described in TSB L-SB-0042-24 for 2024s which have non-functioning massage seats (grey / clear hose)
THE FIX
I bought a pack of 6 more of those hose clamps you can see on the grey / clear hose, and I'm gonna clamp each of the 3 non-barbed fittings I can see. Lexus part number 90466-06001 - Bell Lexus Parts has them online for less than $2 each with free shipping. Unfortunately, this appears to be a Lexus-only part number, so you're gonna have to get it directly from Lexus, though I'm sure a zip tie or other clamps would work the same. I believe you could get away with just clamping the yellow line, but the parts were so cheap I decided to clamp them all.
Simply use your fingers (ONLY - no tools) to unplug the hose, slip the hose clamp onto the hose, reattach it, and move the clamp into place.
Warning: Some of these hoses are very close together. Make sure to position the metal clamp somewhere it isn't touching any hoses, or else the clamp will rub through the hose and you'll get air leaks that way. Triple check to make sure your clamps aren't touching any hoses or wires. I chose not to clamp the clear / grey hose on my passenger side seat (to the left of my finger above) because another hose is routed and touching right where the clamp has to go. Luckily, that appears to be the purge line and it's never under any pressure.
Here's a picture of the back of my passenger seat with 2 out of 3 clamps attached, because I was worried about chafing:
THAT'S IT!
Reinstallation of the seat back is the reverse of removal. Align the seatback, push the top hangers back up into place, reinstall the screws (pro tip - push the seatback upward while screwing it in for less panel gap between the seat and the seatback), and re-hook the elastic.
You did it! Your lumbar should now not deflate at all, and it should also feel significantly stiffer. Now let's go call Lexus to tell them they should have done this at the factory.
