Ford Focus Forum, Ford Focus ST Forum - View Single Post - Oxygen Sensors, OL faults, and crazy volts
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Old 01-20-2013, 01:43 AM  
jetrinka
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That shouldn't happen although its strange that it wouldn't recognize these readings from the O2 sensor and set a code.

The upstream sensor should vary between .2 and .8 volts under ideal conditions quite quickly. What are you using to monitor these voltages? I doubt you can get any good/believable readings from them though as they have to be fairly hot before they can begin working reliably.

The car is supposed to run in open loop for a certain amount of time on a cold startup. What is the history on this car? Have you verified that it has a decent RPM signal while cranking and running, and that it has the basics needed for combustion? After those are verified i'd start looking into whether or not the ECU has all the powers and grounds needed to operate. Its strange that it runs so poorly and doesn't set a code and that is why I say that.
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