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Test NTC-7B - Checking Oxygen Sensor Switching

NOTE: Perform TEST NTC-7A before proceeding.
  1. Start engine. Allow engine to idle. Inspect engine for any abnormal vacuum conditions which may indicate a possible engine mechanical problem. If abnormal vacuum conditions are present, repair engine as necessary. Perform TEST VER-2A. If abnormal vacuum conditions are not present, go to next step.
  2. Using scan tool, read upstream O2S signal voltage. If voltage is .10 volt or more, go to step 4). If voltage is less than .10 volt, go to next step.
  3. Turn ignition off. Disconnect upstream O2S connector. Disconnect PCM connector. Using scan tool in ohmmeter mode, check resistance of upstream O2S signal circuit at connector (harness side). See UPSTREAM O2 SENSOR CONNECTOR WIRE ID (HARNESS SIDE) . If resistance is less than 5 ohms, repair short to ground on upstream O2S signal circuit. Perform TEST VER-2A. If resistance is 5 ohms or more, replace upstream O2S. Perform TEST VER-2A.
  4. Turn engine off. If upstream O2S was already replaced, go to next step. If upstream O2S was not replaced, replace upstream O2S. Go to next step.
  5. Turn ignition on. Using scan tool, reset adaptive fuel memory. Start engine. Allow engine to reach normal operating temperature. Using scan tool, read upstream O2S state. If upstream O2S state is switching LEAN-RICH-LEAN twice or more within 10 seconds, repair is complete. Perform TEST VER-2A. If upstream O2S state is not switching LEAN-RICH-LEAN twice or more within 10 seconds, go to TEST NTC-18A.
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