Toyota prius 3rd gen Occupant Detection ECU (W2)(W3)

Toyota Prius 3 ^rd Generation (XW30)

Occupant Detection ECU Assembly Wiring Guide: DIY Pinout Diagram

What is: The Occupant Detection ECU Assembly is an electronic control unit that works with seat sensors to detect whether a passenger is present and measure their weight. It helps determine if the airbag should deploy and at what force, improving safety during a collision. By analyzing sensor data in real time, it ensures the airbag system operates correctly and prevents unnecessary or unsafe deployments.

Occupant Detection ECU Assembly (89952-47021)

Toyota Prius 3rd gen Occupant Detection ECU 89952-47021 front view

Close-up of Prius 2009–2015 Occupant Detection ECU connector ports

OEM Toyota 89952-47021 passenger seat Occupant Detection module

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1. Introduction

      The   Toyota Prius 3rd Generation Occupant Detection ECU (89952-47021) is a key safety module responsible for managing the passenger seat’s weight-sensing system. It works with the seat airbag sensors and classification mats to identify whether a seat is occupied and determine the passenger’s weight category. This information is then sent to the SRS airbag system to control airbag activation and deployment force. By accurately analyzing real-time data, the ECU helps prevent unintended airbag deployment, ensures proper protection for adults and children, and maintains overall system reliability. Its precise calibration and integration make it an essential component of the Prius safety architecture.

Related parts and Accessories

• SeatOccupant Detection ECU– the control unit that processes sensor signals.
• Seat weight (pressure) sensors – built into the passenger seat cushion to measure load.
• Seat harness and connectors – wiring linking sensors to the ECU.
• Airbag ECU (SRS control module – receives data from the Occupant Detection ECU and manages airbag deployment.
• Passenger airbag ON/OFF indicator light– shows airbag activation status to the driver.

2. Occupant Detection ECU Assembly Wiring Diagram & Pinout

A. Connector Location

• Occupant Detection ECU Position: Under the front passenger seat.
• Connector Type:
  • W2 (12 pin) gray housing
  • W3 (12 pin) black housing

B. Wiring Table

Occupant Detection ECU Assembly (W2) (W3)

W2 TERMINALS OF Occupant Detection ECU Assembly CONECTOR

Terminal No	Symbol (Pin Definition)	Wiring (Color Code) & Color	Electrical Paths
W2-1	1	(G) Green	➔ W4 3 [Front In Weight Detection Sensor Sub–Assembly]
W2-2	2	(LG) Light Green	➔ W6 3 [Front Out Weight Detection Sensor Sub–Assembly]
W2-3	3	(W) White	➔ W1 3 [Rear In Weight Detection Sensor Sub–Assembly]
W2-4	4	(BR) Brown	➔ W7 3 [Rear Out Weight Detection Sensor Sub–Assembly]
W2-5	5	(GR) Gray	➔ W1 1 [Rear In Weight Detection Sensor Sub–Assembly]
W2-6	6	(V) Violet	➔ W7 1 [Rear Out Weight Detection Sensor Sub–Assembly]
W2-7	7	(P) Pink	➔ W4 2 [Front In Weight Detection Sensor Sub–Assembly]
W2-8	8	(L) Blue	➔ W6 2 [Front Out Weight Detection Sensor Sub–Assembly]
W2-9	9	(SB) Sky Blue	➔ W1 2 [Rear In Weight Detection Sensor Sub–Assembly]
W2-10	10	(B) Black	➔ W7 2 [Rear Out Weight Detection Sensor Sub–Assembly]
W2-11	11	(R) Red	➔ W4 1 [Front In Weight Detection Sensor Sub–Assembly]
W2-12	12	(W) White	➔ W6 1 [Front Out Weight Detection Sensor Sub–Assembly]

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W3 TERMINALS OF Occupant Detection ECU Assembly CONECTOR

Terminal No	Symbol (Pin Definition)	Wiring (Color Code) & Color	Electrical Paths
W3-1	1	(W) White	➳ SW1 5 ➳ LS1 59 ➔ 3A 1 ⇔ 3B 73 ➔ 2A 48 ⇔ 2C 18 ➔ 1 2 ➤ (BAT) 7.5A Blade Fuse [ECU–B]
W3-2	2	(GR) Gray	➳ SW1 2 ➳ LS1 58 ➔ 3A 12 ⇔ 3A 48 ➔ L61 7 (SIL) [DLC3]
W3-3	3	(W-B) White/Black	➳ SW1 3 ➔ S20 2 ⬌ S20 10 ➔ ▼ S1 (Ground Point)
W3-4	4	(LG) Light Green	➳ SW1 4 ➔ S1 13 (FSR-) [Center Airbag Sensor Assembly]
W3-5	5	(P) Pink	➔ W5 2 [Front Seat Inner Belt Assembly RH]
W3-6	_	_
W3-7	7	(B) Black	➳ SW1 6 ➳ LS1 60 ➔ 3A 9 ⇔ 3B 84 ➔ 2A 32 ➤ (IG) 10A Blade Fuse [IGN]
W3-8	8	(L) Blue	➳ SW1 1 ➔ S1 12 (FSR+) [Center Airbag Sensor Assembly]
W3-9	9	(G) Green	➔ W5 1 [Front Seat Inner Belt Assembly RH]
W3-10	_	_
W3-11	_	_
W3-12	_	_

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