Air/Fuel (A/F) Heater Relay (ES300 & RX300)

A/F heater relay relay may also be referred to as A/F HTR. A/F HTR is located in fuse/relay box near battery. Constant battery voltage is supplied from battery, through A/F HTR (25-amp) fuse to one side of A/F HTR . When A/F HTR is energized by MREL terminal of Engine Control Module (ECM), A/F HTR provides battery voltage to +B terminal at A/F ratio sensor.