PFI Chart A7 - Left O2 Sensor Not Ready
WARNING: This page is about a different car, the 1990 Cadillac Seville and 1990 Cadillac Eldorado. However, it is still accessible from the selected car via links, so may be relevant.
ECM provides a .45 volt reference to oxygen sensor on circuit No. 412. When warm, a properly operating oxygen sensor will drive .45 volt reference lower (less than .45 volt) to indicate lean mixture and higher (greater than .45 volt) to indicate rich mixture.
NOTE:
Test numbers refer to test numbers on diagnostic chart.
Test Number 1) At key on with oxygen sensor disconnected, parameter ED32 should read .45 volt (nominal). Lower or higher voltage indicates circuit problems.
Test Number 2) ECM compares voltage on circuit No. 412 to ground voltage on circuit No. 413. It is essential that oxygen sensor ground and ECM ground show good continuity (no voltage difference with engine running).