Diagnostic Aids:

The ECM provides a .45 volt reference to O2 sensor on circuit No. 412. When warm, a properly operating O2 sensor will drive the .45 volt reference lower (below .45 volts) to indicate lean mixtures and higher (above .45 volts) to indicate a rich mixture. If under the above test conditions and the O2 sensor does not vary from the "COLD" or "NOT READY" voltage, the ECM assumes that the sensor can not respond to air/fuel mixtures rich or lean. Code "E013" is then set.

NOTE: The following step numbers refer to the numbers in the accompanying flow chart(s).

At key on with O2 sensor disconnected, parameter ED07 should read about .45 volts. Lower or higher voltage indicates circuit problems.
The ECM compares voltage on circuit No. 412 to ground voltage on circuit No. 413. It is essential that the O2 sensor ground and ECM ground on pin D6 show good continuity (no voltage difference) with engine running.