LEMON Manuals: Even more car manuals for everyone: 1960-2025
Home >> Toyota >> 2003 >> Matrix Base, FWD, Automatic >> Repair and Diagnosis >> External Pages >> Different car >> Section 13 (Engine Control System Self-Diagnostics - V6) >> Diagnostic Tests >> DTC P0125: Insufficient Coolant Temperature For Closed Loop Fuel Control >> Diagnosis & Repair
April 5, 2026: LEMON Manuals is launched! Read the announcement.

Diagnosis & Repair

WARNING: This page is about a different car, the 2002 Toyota Highlander. However, it is still accessible from the selected car via links, so may be relevant.
  1. Using Toyota hand-held tester or scan tool, check for any other DTCs. If only DTC P0125 exists, go to next step. If other DTCs exist, diagnose and repair those DTCs first and retest.
  2. With Toyota hand-held tester or scan tool still connected to DLC No. 3, start engine and increase engine speed to 2500 RPM for approximately 90 seconds to fully warm the A/F sensor. Allow engine to idle. Using hand-held tester or scan tool, monitor each A/F sensor output voltage with engine idling, engine racing and while driving vehicle at 25 MPH or more with engine speed of 1500 RPM or more while opening and closing the throttle. Ensure A/F sensor output voltage is as specified. See AIR/FUEL SENSOR OUTPUT VOLTAGE SPECIFICATIONS  table. If voltage is as specified, go to next step. If voltage is not as specified, go to step  9.
    NOTE: If A/F sensor output voltage remains 3.30 volts (Toyota hand-held tester) or .66 volt (OBD-II scan tool) during all conditions, A/F sensor circuit may be open. If A/F sensor output voltage remains 3.80 volts or more (Toyota hand-held tester) or .76 volt or more (OBD-II scan tool) during all conditions, A/F sensor circuit may be shorted. If A/F sensor output voltage remains 2.80 volts or less (Toyota hand-held tester) or .56 volt or less (OBD-II scan tool) during all conditions, A/F sensor circuit may be shorted. During fuel enrichment, A/F sensor output voltage may be less than 2.8 volts (Toyota hand-held tester) or .56 volt (OBD-II scan tool) which is normal. During fuel cut, A/F sensor output voltage may be more than 3.8 volts (Toyota hand-held tester) or .76 volt (OBD-II scan tool) which is normal.
    AIR/FUEL SENSOR OUTPUT 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. Measure resistance between terminal B+ (Red/White wire) and HT (Black/Red wire on bank No. 1; Black wire on bank No. 2) at A/F sensor connector (component side). See Fig 1. Resistance should be 0.8-1.4 ohms at 68°F (20°C) and 1.8-3.2 ohms at 1472°F (800°C). If resistance is as specified, go to next step. If resistance is 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 44-50 psi (3.1-3.5 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 operation of fuel injectors. See FUEL SYSTEMS in SYSTEM & COMPONENT TESTING - V6 & V8 article. Fuel injector volume should be .20-.25 oz. (60-73 cc) every 15 seconds and difference in volume between each fuel injector should be less than .04 oz. (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(s).
  9. Clear DTCs. Perform test drive confirmation, then go to next step. See TEST DRIVE CONFIRMATION .
  10. Using Toyota hand-held tester or scan tool, check for any other 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: Identifying A/F Sensor Connector Terminals
G00027300Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
scientia non olet · About LEMON Manuals