Diagnostic Aids
An intermittent may be caused by a poor connection, rubbed through wire insulation or a wire broken inside the insulation. Check for the following conditions:
- Poor Connection or Damaged Harness. Inspect harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, poor terminal to wire connection and damaged harness.
- Intermittent Test. If connections and harness check okay, observe ED15 display, O2 sensor voltage while moving related connectors and wiring harness, with warm engine running at part throttle in closed loop. If the failure is induced, the O2 sensor voltage reading will change from its normal fluctuating voltage (greater than .60 volt and less than .30 volt) to a fixed value around .45 volt. This may isolate the location of malfunction.