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Home >> Toyota >> 2001 >> Avalon XLS >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System Self-Diagnostics >> Diagnostic Tests >> DTC P0125: Insufficient Coolant Temperature For Closed Loop Fuel Control >> Diagnosis & Repair

Diagnosis & Repair

  1. If only DTC P0125 is displayed, go to next step. If other DTCs are displayed, diagnose and repair those DTCs first and retest system.
  2. Connect scan tool to Data Link Connector (DLC) No. 3. See Figure. Start engine and increase engine speed to 2500 RPM for approximately 90 seconds. Using scan tool, monitor each A/F sensor output voltage. See AIR/FUEL SENSOR VOLTAGE SPECIFICATIONS  table. If voltage is as specified, go to next step. If voltage is not as specified, go to step  9.
    AIR/FUEL SENSOR VOLTAGE SPECIFICATIONS

    Application & Operating Condition Specification
    Using OBD-II Scan Tool
    Engine Idling, Engine Racing & Driving Vehicle (1) (2)
    Using Toyota Hand-Held Tester
    Engine Idling, Engine Racing & Driving Vehicle (1) (3)
    (1) Drive vehicle at 25 MPH or more with engine speed of 1500 RPM or more while opening and closing the throttle.
    (2) Voltage should not remain at .56 volt or less, .66 volt, or .76 volt or more.
    (3) Voltage should not remain at 2.80 volts or less, 3.30 volts, or 3.80 volts or more.
  3. Check for open or short in wiring between ECM and suspect A/F sensor. See WIRING DIAGRAMS article. If problem does not exist, go to next step. If problem exists, repair wiring as necessary.
  4. Disconnect suspect A/F sensor harness connector. A/F sensor for bank 2 is located in exhaust manifold. A/F sensor for bank 1 is located in exhaust pipe in front of catalytic converter. Measure resistance between terminals B+ (Black/White wire) and HT (Black/Red wire) at A/F sensor connector (component side). See Fig 1. Resistance should be .8-1.4 ohms at 68°F (20°C) and 1.8-3.2 ohms at 1472°F (800°C). If resistances are as specified, go to next step. If resistances are not as specified, replace appropriate A/F sensor.
  5. Ensure oil dipstick, oil filler cap, PCV system and all other air induction system components are intact and operating properly. If problem does not exist, go to next step. If problem exists, repair as necessary.
  6. Check fuel pressure. See FUEL SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - V6 & V8 article. Fuel pressure should be 44-55 psi (3.1-3.9 kg/cm2 ) at idle, and should be 21 psi (1.5 kg/cm2 ) or more for 5 minutes after engine has stopped. If fuel pressure is as specified, go to next step. If fuel pressure is not as specified, repair as necessary.
  7. Check fuel injectors. See FUEL SYSTEMS in SYSTEM & COMPONENT TESTING - V6 & V8 article. Fuel injector volume should be 3.7-4.5 Cu. In. (60-73 cc) every 15 seconds and difference in volume between each fuel injector should be less than .8 Cu. In. (13 cc). Fuel injectors should not leak more than one drop every 12 minutes. If problem does not exist, go to next step. If problem exists, repair as necessary.
  8. Check exhaust system for leaks. If problem exists, repair as necessary. If problem does not exist, replace defective A/F sensor.
  9. Clear DTCs. Perform test drive confirmation, then go to next step. See TEST DRIVE CONFIRMATION  under DTC P1130 OR P1150: AIR/FUEL SENSOR CIRCUIT RANGE/PERFORMANCE.
  10. Recheck for DTCs. If DTC P0125 is not displayed again, go to next step. If DTC P0125 is displayed again, replace ECM.
  11. 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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