Note On Intermittents:

If an intermittent Code EO13 is being set, manipulate the related wiring while observing engine data parameter ED07 at part throttle with the engine warm. System should be in "closed loop". If the failure is induced, the oxygen sensor reading will change from its normal fluctuating voltage (above .60 and below .30) to a fixed value around .45 volts. This will help to isolate the location of the malfunction.

Fig 1: Code E013, Open Oxygen Sensor Circuit

Fig 2: Code E013, Schematic