SFI SYSTEM(w/ Canister Pump Module), Diagnostic DTC:P0128

DTC Code DTC Name
P0128 Thermostat

DESCRIPTION

This DTC is stored when the engine coolant temperature does not reach 73°C (163°F) despite sufficient engine warm-up time having elapsed.

DTC No.

Detection Item

DTC Detection Condition

Trouble Area

MIL

Memory

P0128

Thermostat

All of the following conditions are met for 5 seconds (2 trip detection logic):

(a) Cold start

(b) The engine is warmed up

(c) The engine coolant temperature is less than 73°C (163°F)

  • Thermostat

  • Cooling system

  • Engine coolant temperature sensor

  • ECM

Comes on

DTC stored

MONITOR DESCRIPTION

A121605E38

The ECM estimates the engine coolant temperature based on the starting temperature, engine load, and engine speed. The ECM then compares the estimated temperature with the actual engine coolant temperature. When the estimated engine coolant temperature reaches 73°C (163°F), the ECM checks the actual engine coolant temperature. If the actual engine coolant temperature is less than 73°C (163°F), the ECM interprets this as a malfunction in the thermostat or the engine cooling system and stores this DTC.

MONITOR STRATEGY

Frequency of Operation

Once per driving cycle

CONFIRMATION DRIVING PATTERN

A231721E21

  1. Stop the engine and allow it to soak.

  2. Connect the GTS to the DLC3.

  3. Turn the power switch on (IG) and turn the GTS 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. Put the engine in inspection mode (maintenance mode).

    Click here

  7. Set the heater to MAX HOT with fresh air mode selected and turn the A/C off.

  8. Start the engine.

  9. With the engine running, 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.

    Tip:

    If the engine stops, further depress the accelerator pedal to restart the engine.

  10. After "Coolant Temp" stabilizes, check that "Coolant Temp" is 73°C (163°F) or higher [C].

    Tip:

    If "Coolant Temp" is less than 73°C (163°F) while driving the vehicle at 80 km/h (50 mph), inspect the cooling system and thermostat.

CAUTION / NOTICE / HINT

Tip:

  • When the DTC is output, check the engine coolant temperature using the GTS. 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.

  • Read freeze frame data using the GTS. 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 TO DTC P0128)

    1. Connect the GTS to the DLC3.

    2. Turn the power switch on (IG).

    3. Turn the GTS on.

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

    5. Read the DTCs.

      Powertrain > Engine and ECT > Trouble Codes

      Result

      Result

      Proceed to

      DTC P0128 is output

      A

      DTC P0128 and other DTCs are output

      B
      Tip:

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

    B

    GO TO DTC CHART

    Click here

    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 cooling fan operation or any modifications.

    Result

    Proceed to

    OK

    NG
    NG

    REPAIR OR REPLACE COOLING SYSTEM

    OK

  3. INSPECT THERMOSTAT

    1. Inspect the thermostat (thermostat opening temperature).

      Click here

    Result

    Proceed to

    OK

    NG
    NG

    REPLACE THERMOSTAT

    Click here

    OK

  4. INSPECT ENGINE COOLANT TEMPERATURE SENSOR

    1. Inspect the engine coolant temperature sensor.

      Click here

      Tip:

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

      Click here

    Result

    Proceed to

    OK

    NG
    OK

    REPLACE ECM

    Click here

    NG

    REPLACE ENGINE COOLANT TEMPERATURE SENSOR

    Click here