ECM Code EO17: Left Oxygen Sensor Not Ready: Action:

ECM turns on SERVICE ENGINE SOON light and closed loop is disabled.

When warm, a properly operating oxygen sensor will drive the ECM's .45-volt reference signal lower (less than .45 volt) to indicate a lean mixture, and higher (greater than .45 volt) to indicate a rich mixture. If under test conditions the oxygen sensor does not vary from the cold or not ready voltage, ECM assumes sensor can't respond to air/fuel mixture changes and sets a Code EO17.

NOTE: Test numbers refer to test numbers on diagnostic chart.

Test Number 1) A voltage of .42-.48 displayed is a reference from the ECM. Oxygen sensor must generate .15 volt greater than the .45 reference to register a cross count in the ECM.

Test Number 2) The ECM compares voltage on circuit No. 912 to the ground voltage on circuit No. 413. It is essential that oxygen sensor ground and ECM ground on terminal E15 indicate good continuity (no voltage difference) with engine running.