scottmcphee Posted April 25, 2016 Share Posted April 25, 2016 Update: shite! Today, the car codes p2138 on my wife pulling out of the garage. Cold car. I restart the car, check-engine is now off (by itself) and car is driving again. Go for a longer spin... check engine comes on again, but is driveable. I get home and pull codes .. the car is now throwing p0139 rear O2 sensor code "slow to respond" again. The ECM view of rear O2 voltage (using BtSsm tool on OBD port) is pretty much stuck on 0.6v. When I test the O2 sensor itself with VOM, it goes between 0.1 and 0.8 depending on what the car is doing (load, lean, etc..) so the O2 is still responding to gasses just fine. But the ECM is only reporting 0.6v (steady). True values are not arriving or being computed right at ECM. So it seems a "disappearing rear O2 sensor" and "drive by wire sensor disagreement" is a related curse traveling in my car as buddies. The other day, after doing my ground lugs on the block... the ECM was seeing the wider range of voltages from the rear O2 and it wasn't complaining about it. Today, the ghosts are back. Truth be told, when I cleaned the ground lugs, I was pulling and checking all connectors between sensors and ECM, including the main big fat connector on engine block. ... Whatever connection is too soft for rear O2, it is also probably wreaking havoc with my drive by wire sensors in pedal and or throttle body. My guess still, is ... a bad ground somewhere. Something that is common to both of these circuits and sensors in the car. Link to comment Share on other sites More sharing options...
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