Toyota prius 3rd gen stop light control relay assembly (A28)

Toyota Prius 3 ^rd Generation (XW30)

Stop Light Control Relay Assembly Wiring Guide: DIY Pinout Diagram

What is: The Stop Light Control Relay Assembly (also called the Stop Lamp Relay or Brake Light Relay) is an electrical component in a vehicle’s lighting and braking system. It helps control the power supply to the brake lights when you press the brake pedal.

Stop Light Control Relay Assembly (895A0-47020)

Toyota Prius 3rd Gen Stop Light Control Relay (895A0-47020) – Front View

Toyota Prius 3rd Gen stop light control relay assembly 895A0-47020

Genuine Toyota stop light control relay 895A0-47020

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1. Introduction

      The  Toyota Prius 3rd Generation Stop Light Control Relay is a key electrical component that manages the operation of the brake lights. When the brake pedal is pressed, the relay activates to supply power from the battery to the stop lamps, ensuring clear and timely illumination for safety. It works in coordination with the brake pedal switch and wiring system, protecting the circuit from overloads and ensuring reliable brake light performance during vehicle operation.

Related parts and Accessories

• Stop Light Switch (Brake Pedal Switch) – Detects brake pedal movement and sends the activation signal.
• Stop Lamps (Brake Lights) – Illuminate at the rear to indicate braking.
• Fuse (Stop Light Circuit Fuse)– Protects the stop light circuit from electrical overloads.
• Wiring Harness and Connectors – Carry electrical current between the relay, switch, and lamps.
• Relay Block / Junction Block – Houses and supports the stop light control relay.
• Battery and Ground Connections – Supply and complete the electrical circuit for the stop light system.

2. Stop Light Control Relay Assembly Wiring Diagram & Pinout

A. Connector Location

• Stop Light Control Relay Assembly Position: The Stop Light Control Relay is located inside the cabin, under the dashboard, to the left of the steering column.
• Connector Type:
  • A28 (10 pin) Black housing

B. Wiring Table

Stop Light Control Relay Assembly (A28)

A28 TERMINALS OF Stop Light Control Relay Assembly CONECTOR

Terminal No	Symbol (Pin Definition)	Wiring (Color Code) & Color	Electrical Paths
A28-1	OUT	(G) Green	➔ A50 3 ⬌ A50 4 ➳ AR1 5 ➔ R29 8 ⬌ R29 7 ➳ VR1 15 ➔ V14 1 (STP+) [Noise Filter(Stop Light)] ➔ A50 3 ⬌ A50 4 ➳ AR1 5 ➔ R29 8 ⬌ R29 7 ➳ VR1 15 ➔ dV1 2 ➔ d1 2 (B) [Center Stop Light Assembly] ➔ A50 3 ⬌ A50 4 ➳ AR1 5 ➔ R29 8 ⬌ R28 12 ➔ R17 2 (B) [Rear Combination Light Assembly LH] ➔ A50 3 ⬌ A51 4 ➳ AS1 8 ➔ S18 2 (B) [Rear Combustion Light Assembly RH] ➔ A50 3 ⬌ A51 3 ➔ A58 6 (STP2) [Skid Control ECU with Actuator Assembly]
A28-2	_	_	_
A28-3	_	_	_
A28-4	ESSI	(BE) Beige	➔ A58 21 (EXO) [Skid Control ECU with Actuator Assembly]
A28-5	STP (Stop Light Switch)	(L) Blue	➔ A50 10 ⬌ A50 11 ➔ A26 1 [Stop Light Switch Assembly] ➔ A50 10 ⬌ A51 8 ➔ A58 33 (STP) [Skid Control ECU with Actuator Assembly] ➔ A50 10 ⬌ A51 7 ➔ A22 23 (STP) [Power Management Control ECU] ➔ A50 10 ⬌ A50 12 ➳ AL2 6 ➔ L60 1 (STP-) [Driving Support ECU Assembly]
A28-6	+B (Battery Positive)	(R) Red	➔ 2C 12 ➤ (BAT) 10A Blade Fuse [STOP]
A28-7	_	_	_
A28-8	GND ( Ground )	(W-B) White/Black	➔ ▼ A1 (Ground Point)
A28-9	ACC	(Y) Yellow	➔ A58 3 (STPO) [Skid Control ECU with Actuator Assembly]
A28-10	_	_	_

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Quick Pin Summary – A28 Connector

Connector: A28 (10-pin, Black housing)

• A28-1 OUT (Stop Light Output) :
  Supplies power from the relay to all brake lights when activated. Used to illuminate rear stop lamps, center brake light, and send signal outputs. Connected to rear combination lights (LH/RH), center stop light, noise filter, and Skid Control ECU (STP2 via A58-6).
• A28-2 Not Used (—) :
  No connection / not used. No function in this circuit. Not connected.
• A28-3 Not Used (—) :
  No connection / not used. No function in this circuit. Not connected.
• A28-4 ESSI (Emergency Stop Signal Input) :
  Signal line related to emergency braking logic. Used by control systems to detect rapid braking conditions. Connected to Skid Control ECU, connector A58, terminal 21 (EXO).
• A28-5 STP (Stop Light Switch Signal) :
  Input signal from the brake pedal switch. Activates relay when brake pedal is pressed. Connected to Stop Light Switch (A26-1), Skid Control ECU (A58-33), Power Management Control ECU (A22-23), and Driving Support ECU (L60-1).
• A28-6 +B (Battery Power Supply) :
  Main 12V power input to the relay. Provides electrical power for relay operation and output circuit. Connected to battery via 10A STOP fuse.
• A28-7 Not Used (—) :
  No connection / not used. No function in this circuit. Not connected.
• A28-8 GND (Ground) :
  Ground reference for relay operation. Completes the electrical circuit. Connected to chassis ground point A1.
• A28-9 ACC (Accessory / Signal Output) :
  Signal output used for ECU monitoring. Helps control systems detect brake operation status. Connected to Skid Control ECU, connector A58, terminal 3 (STPO).
• A28-10 Not Used (—) :
  No connection / not used. No function in this circuit. Not connected.

Quick Note:The A28 connector of the stop light control relay receives brake input (STP), battery power (+B), and ground (GND) to activate. When triggered, it outputs (OUT) power to all brake lights and communicates with multiple ECUs for braking control and safety monitoring.