Upstream Oxygen Sensors Circuit - P0131, P0132, P0151, P0152

Upstream Oxygen sensors circuit - P0131, P0132, P0151, P0152
This monitors the upstream sensor element current. If the current is above or below a calibrated value, and the stable operating conditions are satisfied, a failure timer is incremented, otherwise a normal timer is incremented. Upon exceeding the calibrated thresholds for either the failure/normal timers, an appropriate failure/normal end judgement is set.