Mr Engineer

Air-Fuel Ratio (AFR) Sensor Wiring – Automotive Component

The image shows a close-up of an Air-Fuel (AF) Sensor, also known as an Air-Fuel Ratio Sensor, which is used in modern vehicles to measure the proportion of air and fuel in the exhaust gases. This information helps the engine control unit (ECU) optimize combustion for better fuel efficiency and lower emissions.

The sensor is connected through a harness with five distinct wires, each serving a specific function:

1. Sensor signal wire (blue) – Sends voltage signals to the ECU.

2. Heater power supply (white) – Supplies current to the sensor's internal heater.

3. Heater ground (white) – Grounds the heater circuit.

4. Sensor ground (black or gray) – Grounds the signal circuit.

5. Reference voltage or secondary signal (yellow) – Supplies reference or additional sensor input to the ECU.

Injector driver