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Toyota Sienna Service Manual: Insufficient Coolant Temperature for Closed Loop Fuel Control

Toyota Sienna Service Manual / 2GR-FE Engine control system / SFI system / Diagnostic trouble code chart / Insufficient Coolant Temperature for Closed Loop Fuel Control

DTC P0125 Insufficient Coolant Temperature for Closed Loop Fuel Control

DESCRIPTION

Refer to DTC P0115

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)
  • Cooling system
  • Engine coolant temperature sensor
  • Thermostat

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 voltage output 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 sets the DTC.

Example: The ECT is 0C (32F) at engine start. After 5 minutes 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 sets the DTC.

MONITOR STRATEGY

MONITOR STRATEGY

TYPICAL ENABLING CONDITIONS

TYPICAL ENABLING CONDITIONS

TYPICAL MALFUNCTION THRESHOLDS

TYPICAL MALFUNCTION THRESHOLDS

WIRING DIAGRAM

Refer to DTC P0115

INSPECTION PROCEDURE

HINT:

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

  1. Connect the intelligent tester to the DLC3.
  2.  Turn the ignition switch to the ON position.
  3.  Turn the tester on.

    (d) Select the following menu items: DIAGNOSIS / ENHANCED OBD II / DTC INFO / CURRENT CODES.

  4.  Read the DTCs.

Result

Result

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

2 INSPECT THERMOSTAT

  1. Remove the thermostat.
  2. Check the valve opening temperature of the thermostat.

Standard: 80 to 84C (176 to 183F)

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

  1.  Reinstall the thermostat

3 CHECK COOLING SYSTEM

  1. 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.

REPLACE ENGINE COOLANT TEMPERATURE SENSOR

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