Note on Intermittents
If an intermittent Code 13 is being set, manipulate the related wiring while observing engine data parameter .0.7 at part throttle with the engine warm, ("open/closed loop" status light should be on). 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 .50 volts. This will help to isolate the location of the malfunction.