Chart A7 - Open Loop Diagnosis

Fig 1: Chart A7 Schematic Open Loop Diagnosis

The ECM provides a .45-volt reference signal to oxygen sensor on circuit No. 412. When oxygen sensor temperature is low, oxygen sensor functions as an open circuit. ECM will keep system in open loop operation until sensor starts to produce a voltage signal. When warm, a properly operating oxygen sensor will produce a voltage from about .1 volt (lean exhaust) to 1.0 volt (rich exhaust).

The oxygen sensor signal voltage will rapidly swing from rich to lean (at least one swing every 2 seconds) if ECM is in good control of air/fuel mixture.

1. If a code was not set, perform OXYGEN SENSOR CIRCUIT CHECK chart prior to continuing diagnosis.
2. Code E13 is intermittent and the remainder of the oxygen sensor circuit has passed inspection. If no problems are found, clear code and road test vehicle. Refer to the DFI ECM TESTS/CODES article in this section (if necessary).
3. Check for fuel contaminated with lead, which would result in oxygen sensor failure.

Fig 2: Flow Chart A7 - Open Loop Diagnosis

Fig 3: Flow Chart A7 - Open Loop Diagnosis