Toyota Tundra Service Manual: Insufficient Coolant Temperature for Closed Loop Fuel Control (P0125)

Toyota Tundra Service Manual / Engine, Hybrid System / 1ur-fe Engine Control / Sfi System / Insufficient Coolant Temperature for Closed Loop Fuel Control (P0125)

DESCRIPTION

  • Refer to DTC P0115 (See page ).

    DTC No.

    DTC Detection Condition

    Trouble Area

    P0125

    Engine Coolant Temperature (ECT) does not reach closed-loop enabling temperature for 20 minutes (this period varies with engine start ECT)

    (2 trip detection logic)

    • ECT sensor
    • Cooling system
    • Water inlet with thermostat sub-assembly

MONITOR DESCRIPTION

The resistance of the ECT sensor varies in proportion to the actual ECT. The ECM supplies a constant voltage to the sensor and monitors the signal output voltage of the sensor. The signal output voltage varies according to the changing resistance of the sensor. After the engine is started, the ECT is monitored through this signal. If the ECT sensor indicates that the engine is not yet warm enough for closed-loop fuel control despite a specified period of time having elapsed since the engine was started, the ECM interprets this as a malfunction in the sensor or cooling system and stores the DTC.

Example:

The ECT is 0°C (32°F) at engine start. After about 1 minute of running time, the ECT sensor still indicates that the engine is not warm enough to begin closed-loop fuel (air-fuel ratio feedback) control. The ECM interprets this as a malfunction in the sensor or cooling system and stores the DTC.

MONITOR STRATEGY

Related DTCs

P0125: Insufficient engine coolant temperature for closed-loop fuel control

Required Sensors/Components (Main)

Water inlet with thermostat sub-assembly, Cooling system

Required Sensors/Components (Related)

Engine coolant temperature sensor and mass air flow meter

Frequency of Operation

Once per driving cycle

Duration

  • 53 seconds: Engine coolant temperature at engine start is (closed-loop engine coolant temperature - 8.33°C ([15°F]) or higher)
  • 105 seconds: Engine coolant temperature at engine start is (closed-loop engine coolant temperature - 19.44°C [35°F]) or higher, and less than (closed-loop engine coolant temperature - 8.33°C [15°F])
  • 20 minutes: Engine coolant temperature at engine start is less than (closed-loop engine coolant temperature - 19.44°C [35°F])

MIL Operation

2 driving cycles

Sequence of Operation

None

TYPICAL ENABLING CONDITIONS

Monitor runs whenever following DTCs not present

P0101, P0102, P0103 (Mass air flow meter)

P0112, P0113 (Intake air temperature sensor)

P0115, P0117, P0118 (Engine coolant temperature sensor)

P0128 (Thermostat)

TYPICAL MALFUNCTION THRESHOLDS

Engine coolant temperature

  • 53 seconds: Engine coolant temperature at engine start is (closed-loop engine coolant temperature - 8.33°C ([15°F]) or higher)
  • 105 seconds: Engine coolant temperature at engine start is (closed-loop engine coolant temperature - 19.44°C [35°F]) or higher, and less than (closed-loop engine coolant temperature - 8.33°C [15°F])
  • 20 minutes: Engine coolant temperature at engine start is less than (closed-loop engine coolant temperature - 19.44°C [35°F])

CONFIRMATION DRIVING PATTERN

  1. Leave the vehicle outside overnight.
  2. Connect the Techstream to the DLC3.
  3. Turn the ignition switch to ON and turn the Techstream on.
  4. Enter the following menu items: Powertrain / Engine and ECT / Data List / Coolant Temp.
  5. Check that the engine coolant temperature is 10°C (50°F) or less.
  6. Clear DTCs (even if no DTCs are stored, perform the clear DTC operation).
  7. Turn the ignition switch off and wait for at least 30 seconds.
  8. Turn the ignition switch to ON and turn the Techstream on.
  9. Start the engine.
  10. Wait 21 minutes or more.
  11. Enter the following menus: Powertrain / Engine and ECT / Trouble Codes.
  12. Read the pending DTCs.

    HINT:

    • If a pending DTC is output, the system is malfunctioning.
    • If a pending DTC is not output, perform the following procedure.
  13. Enter the following menus: Powertrain / Engine and ECT / Utility / All Readiness.
  14. Input the DTC: P0125.
  15. Check the DTC judgment result.

    Tester Display

    Description

    NORMAL

    • DTC judgment completed
    • System normal

    ABNORMAL

    • DTC judgment completed
    • System abnormal

    INCOMPLETE

    • DTC judgment not completed
    • Perform driving pattern after confirming DTC enabling conditions

    N/A

    • Unable to perform DTC judgment
    • Number of DTCs which do not fulfill DTC preconditions has reached ECU memory limit
  16. If the test result is INCOMPLETE or N/A and no pending DTC is output, perform a universal trip and check for permanent DTCs (See page ).

    HINT:

    • If a permanent DTC is output, the system is malfunctioning.
    • If no permanent DTC is output, the system is normal.

WIRING DIAGRAM

Refer to DTC P0115 (See page ).

CAUTION / NOTICE / HINT

HINT:

  • If DTC P0115, P0116, P0117 or P0118 is stored simultaneously with DTC P0125, the Engine Coolant Temperature (ECT) sensor may have an open or short circuit. Troubleshoot those DTCs first.
  • Read freeze frame data using the Techstream. Freeze frame data records the engine condition when malfunctions are detected. When troubleshooting, freeze frame data can help determine if the vehicle was moving or stationary, if the engine was warmed up or not, if the air-fuel ratio was lean or rich, and other data from the time the malfunction occurred.

PROCEDURE

1.

CHECK ANY OTHER DTCS OUTPUT (IN ADDITION TO DTC P0125)

(a) Connect the Techstream to the DLC3.

(b) Turn the ignition switch to ON.

(c) Turn the Techstream on.

(d) Enter the following menus: Powertrain / Engine and ECT / Trouble Codes.

(e) Read DTCs.

Result

Result

Proceed to

P0125 is output

A

P0125 and other DTCs are output

B

HINT:

If any DTCs other than P0125 are output, troubleshoot those DTCs first.

B

GO TO DTC CHART

A

2.

INSPECT WATER INLET WITH THERMOSTAT SUB-ASSEMBLY

(a) Remove the water inlet with thermostat sub-assembly (See page ).

(b) Check the valve opening temperature of the thermostat.

Standard opening temperature:

80 to 84°C (176 to 183°F)

HINT:

In addition to the above check, confirm that the valve is completely closed when the temperature is below the standard.

NG

REPLACE WATER INLET WITH THERMOSTAT SUB-ASSEMBLY

OK

3.

CHECK COOLING SYSTEM

(a) Check for defects in the cooling system that might cause the system to be too cold, such as abnormal radiator fan operation or any modifications.

HINT:

Perform "Inspection After Repair" after replacing the engine coolant temperature sensor (See page ).

OK

REPLACE ENGINE COOLANT TEMPERATURE SENSOR

NG

REPAIR OR REPLACE COOLING SYSTEM

    Throttle / Pedal Position Sensor / Switch "A" Circuit (P0120-P0123,P0220,P0222,P0223,P2135)

    Thermostat (P0128)

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