Toyota Sienna Quiz
2GR-FE Engine control system

Coolant Thermostat (Coolant Temperature Below Thermostat Regulating Temperature)

In this manual: 2GR-FE Engine control system
Introduction — 55Service specifications — 7Maintenance — 7Engine — 264U151e automatic transaxle — 108Transfer — 19Propeller shaft — 8Drive shaft — 14Differential — 16Axle — 18Suspension — 37Tire and wheel — 54Brake control — 141Parking brake — 16Steering Column — 11Power steering — 18Air conditioning — 106Supplemental restraint system — 146Seat belt — 22Theft deterrent — 14Engine immobiliser — 17Cruise control — 65Lighting — 61Wiper and washer — 13Door lock — 42Meter — 28Audio / visual — 94Navigation — 108Park assist / monitoring — 33Horn — 5Garage door opener — 42GR-FE Engine control system — 126Supplemental restraint system — 147Other system — 14Windshield / windowglass — 43Mirror — 23Instrument panel — 6Seat belt — 22Seat — 92Engine hood / door — 104Exterior — 39Interior — 5Sliding roof — 9Multiplex communication — 18Can communication — 23
10steps
~60min
3/5difficulty
Done 0 of 10

DTC P0128 Coolant Thermostat (Coolant Temperature Below Thermostat Regulating Temperature)

HINT: This DTC relates to the thermostat.

DESCRIPTION This DTC is set when the Engine Coolant Temperature (ECT) does not reach 75C (167F) despite sufficient engine warm-up time

DTC No.

DTC Detection Condition

Trouble Area

P0128

 Conditions (a), (b) and (c) are met for 5 seconds (2 trip detection logic):
  1. Cold start
  2. Engine warmed up
  3. ECT less than 75C (167F)
  • Thermostat
  • Cooling system
  • ECT sensor
  • ECM

MONITOR DESCRIPTION

MONITOR DESCRIPTION

The ECM estimates the ECT based on the starting temperature, engine loads, and engine speeds. The ECM then compares the estimated temperature with the actual ECT. When the estimated ECT reaches 75C (167F), the ECM checks the actual ECT. If the actual ECT is less than 75C (167F), the ECM interprets this as a malfunction in the thermostat or the engine cooling system and sets the DTC.

MONITOR STRATEGY

MONITOR STRATEGY
MONITOR STRATEGY

TYPICAL ENABLING CONDITIONS

TYPICAL ENABLING CONDITIONS

TYPICAL MALFUNCTION THRESHOLDS

TYPICAL MALFUNCTION THRESHOLDS

INSPECTION PROCEDURE

HINT: Read freeze frame data using the intelligent tester. The ECM records vehicle and driving condition information as freeze frame data the moment a DTC is stored. When troubleshooting, freeze frame data can be helpful in determining whether the vehicle was running or stopped, whether the engine was warmed up or not, whether the air-fuel ratio was lean or rich, as well as other data recorded at the time of a malfunction

1 CHECK ANY OTHER DTCS OUTPUT (IN ADDITION TO DTC P0128)

  1. Connect the intelligent tester to the DLC3.
  2. Turn the ignition switch to the ON position.
  3. Turn the tester on.
  4. Select the following menu items: DIAGNOSIS / ENHANCED OBD II / DTC INFO / CURRENT CODES.
  5. Read the DTCs.

Result

HINT: If any DTCs other than P0128 are output, troubleshoot those DTCs first.

2 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.

3 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

REPLACE ECM

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