Oxygen sensors are the primary component for measuring A/F ratio. Most vehicles have conventional sensors which have a range of 0 to about 1.1 volts. These sensors have a somewhat slow response time and narrow band or range. The ECU uses the data from this sensor to determine if the mixture is rich or lean. In contrast, a wide-band O2 sensor has a wider range, as it's name implies and is very accurate at determining just how rich or lean the mixture is. This type of sensor usually has 5 wires, some integrated electronics and the input into the ECU is either a 0 to 5 volt range or a -128 to +128 milliamp range. When a vehicle uses a wideband sensor, the ECU is required to support A/F specific data via diagnostics. The OBD2 spec states that vehicles with wideband sensors must output the equivalence ratio (lambda), which can then be converted to A/F ratio. Stricter emissions regulations are driving the OEM's to use more accurate fuel control, requiring the use of wide-band O2 sensors.