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

Engine Hybrid System. Corolla. Zre142 Aze141
2Az-Fe Engine Control. Corolla. Zre142 Aze141

DESCRIPTION

MONITOR DESCRIPTION

MONITOR STRATEGY

TYPICAL ENABLING CONDITIONS

TYPICAL MALFUNCTION THRESHOLDS

CONFIRMATION DRIVING PATTERN

INSPECTION PROCEDURE

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

CHECK COOLING SYSTEM

INSPECT THERMOSTAT

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


DESCRIPTION

HINT:
This DTC relates to the thermostat.
This DTC is set when the engine coolant temperature does not reach 75°C (167°F) despite sufficient engine warm-up time having elapsed.

DTC No.
DTC Detection Condition
Trouble Area
P0128
  1. Conditions (a), (b) and (c) are met for 5 seconds (2 trip detection logic):
  2. (a) Cold start
  3. (b) Engine warmed up
  4. (c) Engine coolant temperature less than 75°C (167°F)
  1. Thermostat
  2. Cooling system
  3. Engine coolant temperature sensor
  4. ECM

MONITOR DESCRIPTION


Corolla. Zre142 Aze141.2Az-Fe Engine Control.Sfi System. Dtc P0128 Coolant Thermostat (Coolant Temperature Below Thermostat Regulating Temperature)

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

MONITOR STRATEGY


Related DTCs
P0128: Coolant Thermostat
Required Sensors/Components (Main)
Thermostat
Engine coolant temperature sensor
Required Sensors/Components (Related)
Intake air temperature sensor
Vehicle speed sensor
Frequency of Operation
Once per driving cycle
Duration
450 seconds
MIL Operation
2 driving cycles
Sequence of Operation
None

TYPICAL ENABLING CONDITIONS


Monitor runs whenever following DTCs are not present
P0010 (VVT Oil Control Valve)
P0011 (VVT System - Advance)
P0012 (VVT System - Retard)
P0016 (VVT System - Misalignment)
P0031, P0032 (Air Fuel Ratio Sensor Heater - Sensor 1)
P0102, P0103 (Mass Air Flow Meter)
P0112, P0113 (Intake Air Temperature Sensor)
P0115, P0117, P0118 (Engine Coolant Temperature Sensor)
P0120, P0121 P0122, P0123, P0220, P0222, P0223, P2135 (Throttle Position Sensor)
P014C, P014D, P015A, P015B, P2195, P2196, P2237, P2238, P2239, P2252, P2253 (Air Fuel Ratio Sensor - Sensor 1)
P0171, P0172 (Fuel System)
P0301, P0302, P0303, P0304 (Misfire)
P0335 (Crankshaft Position Sensor)
P0340 (Camshaft Position Sensor)
P0351, P0352, P0353, P0354 (Igniter)
P0500 (Vehicle Speed Sensor)
Battery voltage
11 V or more
Either of the following conditions 1 or 2 is met:
-
1. All of the following conditions are met:
-
  1. Engine coolant temperature at engine start - Intake air temperature at engine start
-15 to 7°C (-27 to 12.6°F)
  1. Engine coolant temperature at engine start
-10 to 56°C (14 to 133°F)
  1. Intake air temperature at engine start
-10 to 56°C (14 to 133°F)
2. All of following conditions met:
-
  1. Engine coolant temperature at engine start - Intake air temperature at engine start
More than 7°C (12.6°F)
  1. Engine coolant temperature at engine start
56°C (133°F) or less
  1. Intake air temperature at engine start
-10°C (14°F) or more
Accumulated time that vehicle speed is 80 mph (128 km/h) or more
Less than 20 seconds

TYPICAL MALFUNCTION THRESHOLDS


Duration that both of the following conditions (a) and (b) are met
5 seconds or more
(a) Estimated engine coolant temperature
75°C (167°F) or more
(b) Engine coolant temperature sensor output
Less than 75°C (167°F)

CONFIRMATION DRIVING PATTERN


Corolla. Zre142 Aze141.2Az-Fe Engine Control.Sfi System. Dtc P0128 Coolant Thermostat (Coolant Temperature Below Thermostat Regulating Temperature)

  1. Stop the engine and allow it to soak.
  2. Connect the Techstream to the DLC3.
  3. Turn the ignition switch to ON and turn the Techstream on [A].
  4. Enter the following menus: Powertrain / Engine and ECT / Data List / Primary / Coolant Temp and Intake Air.
  5. Check that "Coolant Temp" is 56°C (133°F) or less and "Intake Air" is between 0 and 35°C (32 and 95°F).
  6. Set the heater to MAX HOT with fresh air mode selected and turn the A/C off.
  7. Start the engine and drive the vehicle at 80 km/h (50 mph) for 15 minutes [B].
    CAUTION:
    When performing the confirmation driving pattern, obey all speed limits and traffic laws.
    HINT:
    1. Data can be captured relatively easily by using the snapshot function in the Data List.
    2. Enter the following menus: Data List / Function / Snapshot Configure / Duration / 5 min.
    3. Data capture can be started by using the target point function. For example, setting the target point to an engine speed of 4000 rpm and then racing the engine, etc. to raise the engine speed to a speed of 4000 rpm or higher will cause data capture to start.
  8. After "Coolant Temp" stabilizes, check that "Coolant Temp" is 75°C (167°F) or higher [C].
    HINT:
    If "Coolant Temp" is less than 75°C (167°F) while driving the vehicle at 80 km/h (50 mph), inspect the cooling system and thermostat.

INSPECTION PROCEDURE

HINT:
  1. 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.
  2. When the DTC is output, check the engine coolant temperature using the Techstream. Enter the following menus: Powertrain / Engine and ECT / Data List / Primary / Coolant Temp. If the Coolant Temp value is lower than the actual engine coolant temperature, the engine coolant temperature sensor circuit may be malfunctioning. In this case, check the wire harnesses and connectors (and those connections) between the ECM and the engine coolant temperature sensor first.
1.CHECK ANY OTHER DTCS OUTPUT (IN ADDITION TO DTC P0128)

  1. Connect the Techstream to the DLC3.

  1. Turn the ignition switch to ON.

  1. Turn the Techstream on.

  1. Enter the following menus: Powertrain / Engine and ECT / Trouble Codes.

  1. Read DTCs.

    Result:

    Result
    		Proceed to
    P0128
    		A
    P0128 and other DTCs
    		B
    HINT:
    If any DTCs other than P0128 are output, troubleshoot those DTCs first.


B
GO TO DTC CHART (COROLLA_ZRE142 RM000000PDF0G9X.html)
A


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.



NG
REPAIR OR REPLACE COOLING SYSTEM
OK


3.INSPECT THERMOSTAT

  1. Remove the thermostat (COROLLA_ZRE142 RM0000017WE03UX.html).

  1. Measure the valve opening temperature of the thermostat.

    Standard Value:
    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.

  1. Reinstall the thermostat (COROLLA_ZRE142 RM0000017WB03UX.html).



NG
REPLACE THERMOSTAT (COROLLA_ZRE142 RM000001X9702FX.html)
OK

REPLACE ECM (COROLLA_ZRE142 RM000002WT402ZX.html)