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

Engine Hybrid System. Yaris. Ncp93, 131
1Nz-Fe Engine Control. Yaris. Ncp93, 131

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)

READ VALUE USING TECHSTREAM (COOLANT TEMP)

CHECK COOLING SYSTEM

INSPECT THERMOSTAT

INSPECT ENGINE COOLANT TEMPERATURE SENSOR

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


DESCRIPTION

HINT:
This DTC relates to the thermostat.
This DTC is stored when the Engine Coolant Temperature (ECT) 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) met for 5 seconds (2 trip detection logic):
  2. (a) Cold start
  3. (b) Engine warmed up
  4. (c) ECT less than 75°C (167°F)
  1. Thermostat
  2. Cooling system
  3. ECT sensor
  4. Wire harness or connector
  5. ECM

MONITOR DESCRIPTION


Yaris. Ncp93, 131.1Nz-Fe Engine Control.Sfi System (For Sedan). Dtc P0128 Coolant Thermostat (Coolant Temperature Below Thermostat Regulating Temperature)

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 75°C (167°F), the ECM checks the actual ECT. If the actual ECT 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
Required Sensors/Components (Related)
Engine Coolant Temperature (ECT) sensor, Intake Air Temperature (IAT) sensor, Vehicle speed sensor
Frequency of Operation
Once per driving cycle
Duration
900 seconds
MIL Operation
2 driving cycles
Sequence of Operation
None

TYPICAL ENABLING CONDITIONS


Monitor runs whenever following DTCs not present
P0010 (VVT OCV )
P0011 (VVT System 1 - Advance)
P0012 (VVT System 1 - Retard)
P0016 (VVT system 1 - misalignment)
P0031, P0032 (A/F sensor heater)
P0100, P0102, P0103 (MAF meter)
P0110, P0112, P0113 (IAT sensor)
P0115, P0117, P0118 (ECT sensor)
P0120 - P0123, P0220, P0222, P0223, P2135 (TP sensor)
P0171, P0172 (Fuel system)
P0301 - P0304 (Misfire)
P0335 (CKP sensor)
P0340 (CMP sensor)
P0351 - P0354 (Ignitor)
P0500 (VSS)
P2195, P2196 (A/F sensor)
P2237 - P2239, P2252, P2253 (A/F sensor)
P2A00 (A/F sensor)
Battery voltage
11 V or more
Either of following conditions 1 or 2 met:
-
1. All of following conditions met:
-
  1. ECT at engine start - IAT at engine start
-15°C to 7°C (-27°F to 12.6°F)
  1. ECT at engine start
-10°C to 56°C (14°F to 133°F)
  1. IAT at engine start
-10°C to 56°C (14°F to 133°F)
2. All of following conditions met:
-
  1. ECT at engine start - IAT at engine start
More than 7°C (12.6 °F)
  1. ECT at engine start
56°C (133°F) or less
  1. IAT at engine start
-10°C (14°F) or more
Accumulated time at 128 km/h (80 mph) or more of vehicle speed
Less than 20 seconds

TYPICAL MALFUNCTION THRESHOLDS


Duration that both following conditions (a) and (b) met
5 seconds or more
(a) Estimated ECT
75°C (167°F) or more
(b) ECT sensor output
Below 75°C (167°F)

CONFIRMATION DRIVING PATTERN


Yaris. Ncp93, 131.1Nz-Fe Engine Control.Sfi System (For Sedan). 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 menu items: Powertrain / Engine and ECT / Data List / 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 (0 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 menu: Data List / Function / Snap-shot configuration / Record time / 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 more 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 below 75°C (167°F) while driving the vehicle at 80 km/h (50 mph), inspect the cooling system and thermostat.

INSPECTION PROCEDURE

HINT:
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.
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
    Display (DTC Output)
    		Proceed To
    DTC P0128 is output
    		A
    P0128 and P0115, P0117, or P0118
    		B


B
GO TO DTC CHART (YARIS_NCP93 RM000000PDF0E6X.html)
A


2.READ VALUE USING TECHSTREAM (COOLANT TEMP)

  1. Connect the Techstream to the DLC3.

  1. Turn the ignition switch to ON.

  1. Turn the Techstream on.

  1. Clear DTCs (YARIS_NCP93 RM000000PDK0QGX.html).

  1. Turn the ignition switch off and wait for at least 30 seconds.

  1. Turn the ignition switch to ON.

  1. Enter the following menus: Powertrain / Engine and ECT / Data List / Coolant Temp.

  1. Read the values displayed on the Techstream while wiggling the ECM wire harness.

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

  1. Read DTCs.

    Result
    Result
    		Proceed to
    Value in Data List changes when wire harness is wiggled, or DTC is output*
    		B
    Other than above
    		A
    *: As the DTC was stored due to a change in the contact resistance of the connector, repair or replace the wire harness or connector (YARIS_NCP93 RM000000UZ309WX.html).
    HINT:
    Check that the actual engine coolant temperature and the Coolant Temp value displayed on the Techstream are approximately equal. If the Coolant Temp value is lower than the actual, check the connector connections between the ECM and the engine coolant temperature sensor.


B
REPAIR OR REPLACE HARNESS OR CONNECTOR (ENGINE COOLANT TEMPERATURE SENSOR - ECM)
A


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.



NG
REPAIR OR REPLACE COOLING SYSTEM
OK


4.INSPECT THERMOSTAT

  1. Remove the thermostat (YARIS_NCP93 RM000001DGA00ZX.html).

  1. Check the valve opening temperature of the thermostat.

    Standard:
    80°C to 84°C (176°F 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 (YARIS_NCP93 RM000001DG700ZX.html).



NG
REPLACE THERMOSTAT (YARIS_NCP93 RM000001DGA00ZX.html)
OK


5.INSPECT ENGINE COOLANT TEMPERATURE SENSOR

  1. Inspect the engine coolant temperature sensor (YARIS_NCP93 RM000001DBF01ZX.html).



NG
REPLACE ENGINE COOLANT TEMPERATURE SENSOR (YARIS_NCP93 RM000001DBH011X.html)
OK

REPLACE ECM (YARIS_NCP93 RM000001CN002AX.html)