An oxygen sensor heater control determines heater activation based on an open-loop
control parameter and a correction factor that compensates for part-to-part variability.
Following a cold start where the heater temperature can be reliably estimated,
the engine controller predicts the resistance of the heating element and heater
circuit at the desired operating temperature of the sensor, and computes the correction
factor for heater activation based on the predicted resistance values and nominal
resistance values. At least one predicted value is stored in non-volatile memory,
and used to compute the correction factor following a warm or hot start of the engine.