A diagnostic apparatus applied to {TAIL ~ internal combustion engine exhaust gas sensors} employing electrochemical polarographic principles indicates sensor operation relative to {HEAD ~ a current limiting operating region} in which a sensor output signal indicates oxygen concentration in the exhaust gas 
A diagnostic apparatus applied to { TAIL ~ internal combustion engine exhaust gas sensors } employing electrochemical polarographic principles indicates sensor operation relative to { HEAD ~ a current limiting operating region } in which a sensor output signal indicates oxygen concentration in the exhaust gas
OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH