• IDL contacts must be off (throttle open).
When these conditions have been satisfied, the voltage signal on the VF terminal will imitate the oxygen sensor signal. Whenever the oxygen sensor signal is high, indicating a rich exhaust condition, the VF terminal voltage will be 5 volts. When the oxygen sensor signal is low, indicating a lean exhaust condition, the VF terminal voltage will be 0 volts.
At 2500 rpm, oxygen sensor switching should occur a minimum of eight times in ten seconds if the closed loop system is operating normally. To test, the engine must be fully warmed up and run at 2500 rpm for one minute to ensure the oxygen sensor has reached operating temperature.
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