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Home >> Toyota >> 1998 >> Tercel Standard >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System Tests W/Codes >> Self-Diagnostic Tests >> DTC P0125: Insufficient Coolant Temperature For Closed Loop Fuel Control >> Diagnosis & Repair
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Diagnosis & Repair

  1. Connect scan tool to DLC No. 3 connector. See Figure. Start vehicle and warm engine to normal operating temperature. Using scan tool, monitor sensor No. 1. Snap accelerate engine 3 times to about 4000 RPM. Sensors should indicate a rich signal (.45 volt or more) at least once.
  2. If a rich signal is indicated at least once, replace ECM. If sensor does not display a rich signal at least once, check for open or short circuit in wiring harness between ECM and suspect sensor. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair wiring as necessary. If wiring harness is okay, go to next step.
  3. Check exhaust system for leaks. Repair as necessary. If exhaust system is okay, replace heated oxygen sensor.
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