4th-gen Sienna (2021+): Removing 2nd-Row Seats

By Brad Ling

Here's everything you need to know about removing the 2nd-row seats on the 4th-generation (2021-2026) Toyota Sienna, and resolving the airbag issue it causes.

The Situation

The last-gen Siennas' 2nd-row seats (2011-2020) were easily removable by pulling a latch. But on the latest Siennas (2021+), they're not user-removable, at least according to Toyota. This is in part because there are now SRS airbags inside the backrests, as seen in this crash test video.

Instead of a quick-release mechanism, the 2nd-row seats are now secured with 4 bolts hidden behind plastic trim pieces. There are also connectors between the seats and the floor for the airbags etc.

The Procedure

I made this video to show the process for removing the 2nd-row seats, which involves:

disconnecting the 12V battery to temporarily depower the airbag system;
prying off seat trim;
disconnecting the airbag and seat heater/seatbelt connectors;
and removing 4 bolts.

The video focuses on 7-passenger Sienna's captain chairs, but the 8-passenger's bench seat has a similar procedure. Its connectors are at the base of the right seat and the corner of the middle cupholder.

More Written Instructions

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The Problem

When any 2nd-row seats are removed, you will see this error:

The car knows that one or more of its airbags are missing. The warning stays over the gauge cluster screen and also appears on the infotainment screen.

You may have heard from technicians or service advisors, "whenever you see this error, it means the entire airbag system is disabled". Although airbag systems are not designed to behave in this all-or-nothing way, it is a prudent assumption, because the warning doesn't specify which part of the airbag system is malfunctioning. Just by observing this warning, we can't know for sure whether it's just complaining about the removed seats, or there's some other malfunction (such as a worn-out clock spring, damaged wiring, or faulty sensor). We must avoid a “cry wolf” situation where, by always assuming this warning is just about the removed seats, we fail to discover if a different SRS component ever malfunctions in the future, jeopardizing safety.

The Solution

Use an airbag emulator to filter out the "cry wolf" errors. The SRS warning will be gone during normal operation, but if there's ever a different SRS problem in the future, it will come up and you'll know about it.

Because each dongle has the same 2.2Ω resistance as the airbag, it's indistinguishable from the original airbag to the vehicle, so the rest of the SRS's function is unaffected and preserved.