1966 Crown Coupe, 2016 200 S AWD, 1962 Lark Daytona V8.
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17,292 Posts
Has it ever set O2 sensor fault codes? The PCM is a better tester of the O2 sensors than any manual test, which is more of a general test.
The downstream may straighten out after a long drive. See what its range is after it's hot and working for awhile. The downsteam O2 will change voltage up/down at about half the rate of speed than the upstream O2 sensor.
The O2's are inactive while cold, so I can't say whether 0 volts is bad or not. The PCM doesn't use the O2 sensor and the O2 heater should be on full until closed loop (~600°F/316°C) anyways, so I don't see the element cold test being a validation.
The downstream may straighten out after a long drive. See what its range is after it's hot and working for awhile. The downsteam O2 will change voltage up/down at about half the rate of speed than the upstream O2 sensor.
The O2's are inactive while cold, so I can't say whether 0 volts is bad or not. The PCM doesn't use the O2 sensor and the O2 heater should be on full until closed loop (~600°F/316°C) anyways, so I don't see the element cold test being a validation.