If the 02 sensor is unplugged and you are reading a scan tool from the diagnostic link then of course the 02 reading is wrong
if you are using a volt meter right at the connector thats on the sensor then the 02 will read lean because the heating elements in it are disconnected when you unplug it
check 02 voltage with engine warmed up and 02 sensor connected you will have to pierce insulation with your probe
Potential causes of an P0156 code
include:
If you have access to a scan tool, check
the signal voltage for the Bank 2,2 oxygen sensor with the engine at normal
operating temperature. Is it stuck low currently? If so, increase RPM for a few
seconds and see if it affects the reading. If it begins working with increased
RPM, check for holes in the exhaust near the o2 sensor that may cause a false
lean. If the exhaust pipe is intact, the sensor is sluggish, replace it.
If the Bank 2,2 o2 sensor voltage reading remains low with increased RPM, unplug it and then observe the reading. It should have increased to about 0.5 volts or thereabouts. If it did, check for water intrusion or other connector problems. If none are found, replace the shorted o2 sensor. If the voltage reading is still stuck low after unplugging the sensor, then suspect a wiring problem. Using a voltmeter, with the o2 sensor unplugged, check for voltage on the signal circuit at the o2 sensor connector(PCM side). It can vary with model, but should be about 0.5 volts and not above 1 volt. If the voltage reading is too high, repair short to voltage on signal circuit. If the signal voltage checks out, suspect the PCM.
329 views
Usually answered in minutes!
×