# What causes an O2 heater circuit malfunction on a IS 300?

The oxygen sensor is "done". It should be replaced.

### A 75 ohm light and a 150 ohm heater are connected in parallel to a 150 volt power source What is the current through the circuit?

The effective resistance of two parallel resistances is (AB)/(A+B) = (75 x 150) / (225) = 50 ohms. Current = (Voltage) / (Resistance) = (150/50) = 3 Amperes. Check, and more details: Current through the 75-ohms = 150 / 75 = 2 Amp. Current through the 150 ohms = 150 / 150 = 1 Amp. Total current from the power supply = 2 + 1 = 3 Amp. Notice that the power dissipated by the…