Lexus RX (RX 350L, RX450h) 2016-2024 Repair Manual: Insufficient Coolant Temperature for Closed Loop Fuel Control (P012500)

Lexus RX (RX 350L, RX450h) 2016-2024 Repair Manual / Engine & Hybrid System / 2gr-fks (engine Control) / Sfi System / Insufficient Coolant Temperature for Closed Loop Fuel Control (P012500)

DESCRIPTION

Refer to DTC P011511.

Click here

DTC No.

Detection Item

DTC Detection Condition

Trouble Area

MIL

Memory

Note

P012500

Insufficient Coolant Temperature for Closed Loop Fuel Control

The engine coolant temperature does not reach the closed loop enabling temperature for 20 minutes (this period varies with the engine coolant temperature at engine start) (2 trip detection logic).
  • Engine cooling system
  • Engine coolant temperature sensor
  • Water inlet with thermostat sub-assembly

Comes on

DTC stored

SAE Code: P0125

MONITOR DESCRIPTION

The resistance of the engine coolant temperature sensor varies in proportion to the actual engine coolant temperature. 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 engine coolant temperature is monitored by this signal. If the engine coolant temperature 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 engine cooling system and stores the DTC.

MONITOR STRATEGY

Related DTCs

P0125: Insufficient engine coolant temperature for closed loop fuel control

Required Sensors/Components (Main)

Engine coolant temperature sensor

Water inlet with thermostat sub-assembly

Engine cooling system

Required Sensors/Components (Related)

-

Frequency of Operation

Once per driving cycle

Duration

69 seconds: Engine coolant temperature at engine start is (closed-loop engine coolant temperature - 8.33°C [46.994°F]) or higher

157 seconds: Engine coolant temperature at engine start is (closed-loop engine coolant temperature - 19.44°C [66.992°F]) or higher, and less than (closed-loop engine coolant temperature - 8.33°C [46.994°F])

1200 seconds: Engine coolant temperature at engine start is less than (closed-loop engine coolant temperature - 19.44°C [66.992°F])

MIL Operation

2 driving cycles

Sequence of Operation

None

TYPICAL ENABLING CONDITIONS

Monitor runs whenever the following DTCs are not stored

None

All of the following conditions are met

-

Thermostat fail (P0128)

Not detected

Intake air temperature sensor circuit fail (P0112, P0113)

Not detected

Engine coolant temperature sensor circuit fail (P0117, P0118)

Not detected

Mass air flow meter circuit fail (P0102, P0103)

Not detected

TYPICAL MALFUNCTION THRESHOLDS

Time until actual engine coolant temperature reaches closed loop fuel control enabling temperature

69 seconds: Engine coolant temperature at engine start is (closed-loop engine coolant temperature - 8.33°C [46.994°F]) or higher

157 seconds: Engine coolant temperature at engine start is (closed-loop engine coolant temperature - 19.44°C [66.992°F]) or higher, and less than (closed-loop engine coolant temperature - 8.33°C [46.994°F])

1200 seconds: Engine coolant temperature at engine start is less than (closed-loop engine coolant temperature - 19.44°C [66.992°F])

CONFIRMATION DRIVING PATTERN

HINT:

  • After repair has been completed, clear the DTC and then check that the vehicle has returned to normal by performing the following All Readiness check procedure.

    Click here

  • When clearing the permanent DTCs, refer to the "CLEAR PERMANENT DTC" procedure.

    Click here

  1. Leave the vehicle outside overnight.
  2. Connect the Techstream to the DLC3.
  3. Turn the engine switch on (IG).
  4. Turn the Techstream on.
  5. Enter the following menus: Powertrain / Engine / Trouble Codes.
  6. Read the DTC and record the Freeze Frame Data.
  7. Clear the DTCs (even if no DTCs are stored, perform the clear DTC procedure).
  8. Enter the following menus: Powertrain / Engine / Data List / Coolant Temperature.
  9. Check that Coolant Temperature is the same or less than Initial Engine Coolant Temperature in the freeze frame data.
  10. Turn the engine switch off and wait for at least 30 seconds.
  11. Start the engine [A].
  12. Turn the Techstream on.
  13. Wait 21 minutes or more [B].
  14. Enter the following menus: Powertrain / Engine / Trouble Codes [C]..
  15. 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.
  16. Enter the following menus: Powertrain / Engine / Utility / All Readiness.
  17. Input the DTC: P012500.
  18. Check the DTC judgment result.

    Techstream 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

    HINT:

    • If the judgment result is NORMAL, the system is normal.
    • If the judgment result is ABNORMAL, the system is malfunctioning.
    • If the judgment result is INCOMPLETE, let the engine cool down (engine coolant temperature is below 5°C (41°F)), and then perform steps [A] and [C]: Normal judgment procedure.

      The normal judgment procedure is used to complete DTC judgment and also used when clearing permanent DTCs.

    • When clearing the permanent DTCs, do not disconnect the cable from the battery terminal or attempt to clear the DTCs during this procedure, as doing so will clear the universal trip and normal judgment histories.

WIRING DIAGRAM

Refer to DTC P011511.

Click here

CAUTION / NOTICE / HINT

HINT:

  • If any of DTCs P011511 or P011515 are output simultaneously with DTC P012500, the engine coolant temperature sensor may have an open or a short circuit. Troubleshoot those DTCs first.
  • Read freeze frame data using the Techstream. The ECM records vehicle and driving condition information as freeze frame data the moment a DTC is stored. 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 DTC P012500)

(a) Connect the Techstream to the DLC3.

(b) Turn the engine switch on (IG).

(c) Turn the Techstream on.

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

(e) Read the DTCs.

Powertrain > Engine > Trouble Codes

Result

Proceed to

DTC P012500 is output

A

DTC P012500 and other DTCs are output

B

HINT:

If any DTCs other than P012500 are output, troubleshoot those DTCs first.

B

GO TO DTC CHART

A

2.

INSPECT WATER INLET WITH THERMOSTAT SUB-ASSEMBLY

(a) Inspect the water inlet with thermostat sub-assembly (thermostat opening temperature).

Click here

NG

REPLACE WATER INLET WITH THERMOSTAT SUB-ASSEMBLY

OK

3.

CHECK ENGINE COOLING SYSTEM

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

HINT:

Perform "Inspection After Repair" after replacing the engine coolant temperature sensor.

Click here

OK

REPLACE ENGINE COOLANT TEMPERATURE SENSOR

NG

REPAIR OR REPLACE ENGINE COOLING SYSTEM
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