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Home >> Toyota >> 2000 >> RAV4 Base, AWD, Automatic >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System Self-Diagnostics >> Diagnostic Tests >> DTC P0125: Insufficient Coolant Temperature For Closed Loop Fuel Control (CALIF. Emissions) >> Diagnosis & Repair
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Diagnosis & Repair

  1. If any other DTCs are displayed, diagnose and repair those DTCs first and retest system. If only DTC P0125 is displayed, go to next step.
  2. Connect scan tool to Data Link Connector (DLC) No. 3. Start engine and increase engine speed to 2500 RPM for approximately 90 seconds. Using scan tool, monitor A/F sensor output voltage. See AIR/FUEL RATIO SENSOR VOLTAGE SPECIFICATIONS  table. If voltage is as specified, go to next step. If voltage is not as specified, go to step  10.
    AIR/FUEL RATIO SENSOR VOLTAGE SPECIFICATIONS

    Application (1) Volts
    Using OBD-II Scan Tool
    Engine Idling 0.66
    Engine Racing 0.76 Or More
    Driving Vehicle (2) 0.56 Or Less
    Using Toyota Hand-Held Tester
    Engine Idling 3.3
    Engine Racing 3.8 Or More
    Driving Vehicle (2) 2.8 Or Less
    (1) Voltage should not remain constant at specification given.
    (2) Drive vehicle at 25 MPH or more, with engine speed at 1500 RPM or more, while opening and closing throttle valve.
  3. Check for open or short in wiring between ECM and A/F sensor. See WIRING DIAGRAMS article. If problem exists, repair wiring as necessary. If problem does not exist, go to next step.
  4. Disconnect A/F sensor harness connector. Measure resistance between terminal B+ (Black/Red wire) and HT (Red wire) at A/F sensor connector (component side). See Fig 1. Resistance should be .8-1.4 ohms at 68°F (20°C). If resistance is not as specified, replace A/F sensor. If resistance is as specified, go to next step.
  5. Ensure oil dipstick, oil filler cap, PCV system and all other air induction system components are intact and operating properly. If problem exists, repair as necessary. If problem does not exist, go to next step.
  6. Check EGR system components. See EMISSION SYSTEMS & SUB-SYSTEMS in SYSTEM & COMPONENT TESTING - 4-CYLINDER article. If problem exists, repair as necessary. If problem does not exist, go to next step.
  7. Check fuel pressure. See FUEL SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - 4-CYLINDER article. If fuel pressure is not within specification, repair as necessary. If fuel pressure is within specification, go to next step.
  8. Check fuel injectors. See FUEL SYSTEMS in SYSTEM & COMPONENT TESTING - 4-CYLINDER article. If problem exists, repair as necessary. If problem does not exist, go to next step.
  9. Check exhaust system for leaks. If problem exists, repair as necessary. If problem does not exist, replace defective A/F sensor.
  10. Perform test drive confirmation, then go to next step. See TEST DRIVE CONFIRMATION  under DTC P1130: AIR/FUEL SENSOR CIRCUIT RANGE/PERFORMANCE MALFUNCTION (CALIF. EMISSIONS).
  11. Clear and recheck for DTCs. If DTC P0125 is displayed again, replace ECM. If DTC P0125 is not displayed again, go to next step.
  12. Vehicle either ran out of fuel or problem is intermittent. Check component and ECM connections.
Fig 1: Testing A/F Sensor Heater
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