O2 sensor voltage

[krakoosh]

Does any one know what the voltage should be for the O2's according to a scan tool at idle? Trying to track down a PO171 code. If I spray into a vacuum line they both max out which should mean they're working. On the scan tool they both jump all over the place...should they read a steady #?

 

[docraymund]

The normal voltage is between 0.2 and 0.9 volts. If it fluctuates you may have a vacuum leak or a leaky fuel injector.

 

[stamp11127]

The upstream O2 sensor(s) cycle between lean & rich, the downstream should stay fairly steady if the cat is doing its job.

 

[krakoosh]

Thank you both. It looks like they're working fine then.