U0154 is the airbag sensor assembly reporting that it can no longer reach the occupant detection ECU over CAN. Toyota and Lexus print it with the information code 99 on some models. That ECU decides whether the front passenger seat holds an adult, a child, or nothing at all, so the passenger airbag ON and OFF indicator usually behaves oddly while the code is stored.
The Lexus repair manual gives U0154 the description Lost Communication with Restraints Occupant Classification System Module. The detection condition reads as a CAN communication error between the airbag sensor assembly and occupant detection ECU. The trouble area listed is the CAN communication system, and the manual sends the technician to the CAN troubleshooting section rather than to a restraint part.
The occupant detection ECU lives under the front passenger seat and reads the sensors built into the seat cushion. It classifies the occupant and reports that classification to the airbag sensor assembly, which then arms or suppresses the passenger frontal airbag. When the two stop talking, the system has no classification to work from and the airbag warning light comes on.
One detail matters before any part is ordered. Toyota and Lexus require zero point calibration when the occupant detection ECU is replaced, when the front passenger seat is removed, and even when one of the seat mounting bolts is taken out. That procedure runs at the vehicle with a scan tool, on level ground, with nothing on the seat.
Communication. U0154 records a conversation that stopped, so it holds no deployment data and names no failed part on its own. After a collision the code can appear alongside stored crash data, because floor and seat harnesses take damage in the same impact that deploys the bags. Treat the two findings as separate jobs: repair the wiring, then deal with whatever the airbag sensor assembly has locked in memory.
No. A module reset restores stored memory and has no effect on a CAN circuit that is open or a module that has stopped answering. Repair the connection, clear the codes, and cycle the key to confirm.
If the airbag sensor assembly also locked after a collision, that is the part our airbag module reset handles. When the seat sensing hardware turns out to be the failure, we list genuine OEM occupant classification sensors. Zero point calibration still has to be performed at the vehicle after the seat goes back in.
U0154 sits in the generic SAE U0 range, which means Toyota and Lexus share the number with other manufacturers that assign it to their own occupant classification module. The wording on this page follows Toyota and Lexus service data for vehicles with a separate occupant detection ECU, which covers RX, ES, and NX along with the Toyota models built beside them. Read the code with the make in hand before ordering a part.
Slide the passenger seat forward and back and look underneath first. The connector at the occupant detection ECU and the harness running to it are the two things disturbed by seat removal, carpet cleaning, and cargo sliding under the seat. Unplug the connector, check the terminals for spread pins and corrosion, and reseat it.
Then scan every module. If the airbag sensor assembly is the only one reporting a lost communication code, the fault is local to that branch. If several modules report U codes, chase the bus itself. Related codes on the same system include B1650 for an occupant classification malfunction reported to the airbag ECU, plus B1790 on the communication circuit between the occupant classification ECU and the airbag sensor assembly and B1794 on that ECU's battery line. If the part you need is not listed, send us a part request.
Related codes: B1650, B1790, B1794
Keep reading:
Code scope: Lexus. The same number can mean something different on another manufacturer, so match the code to your make before you act on it.
A reset clears stored crash data. A replacement part fixes a hardware fault. We have read these codes since the nineties and will tell you which one you are looking at.
Genuine OEM, tested, and shipped ground from Jacksonville, Arkansas.
Lexus parts and codes · Do not see it listed? Request a part or call 501-988-0611.