1.CHECK HARNESS BETWEEN ECM AND FRONT OXYGEN (A/F) SENSOR CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connectors from the ECM and front oxygen (A/F) sensor.
3) Measure the resistance of harness between ECM and front oxygen (A/F) sensor connector.
Connector & terminal
(B135) No. 9 — (E23) No. 1:
(B135) No. 8 — (E23) No. 3:
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Is the resistance less than 1 Ω?
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Repair the harness and connector.
NOTE:
In this case, repair the following item:
• Open circuit in harness between ECM and front oxygen (A/F) sensor connector
• Poor contact of coupling connector
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2.CHECK FOR POOR CONTACT.
Check poor contact of ECM and front oxygen (A/F) sensor connector.
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Is there poor contact in ECM or front oxygen (A/F) sensor connector?
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Repair the poor contact of ECM or front oxygen (A/F) sensor connector.
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Replace the front oxygen (A/F) sensor. 
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