97Ford ranger 4.0. I'm looking into a p0420. Believe the cat to be bad on this. Fully warmed up at idle the rear o2 Voltage is 0. 1500rpm it will start oscillating like the upstream. Return the engine back to idle rear o2 goes back to 0 Volts. Adding propane at Idle drives the o2 Rich. Is the 0 volts at idle fully warmed up normal?
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