Chart A6 - Open Loop Diagnosis (O2 Sensor Not Ready)

The ECM provides a .45 volt reference to oxygen sensor on circuit No. 412. When warm, a properly operating oxygen 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.

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

At key on with oxygen sensor disconnected, parameter "ED07" should read .45 volts (nominal). 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 oxygen sensor ground and ECM ground on pin D6 show good continuity with no voltage difference with engine running.

Fig 1: Flow Chart A6 - Open Loop Diagnosis - O2 Sensor Not Ready

Fig 2: Flow Chart A6 - Open Loop Diagnosis - O2 Sensor Not Ready (1 of 3)

Fig 3: Flow Chart A6 - Open Loop Diagnosis - O2 Sensor Not Ready (2 of 3)

Fig 4: Flow Chart A6 - Open Loop Diagnosis - O2 Sensor Not Ready (3 of 3)