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DTC P0128

DTC P0128  : Cooling System Malfunction

NOTE: Before you troubleshoot, record all freeze data and any on-board snapshot, and review the general troubleshooting information .
DTC Description Confirmed DTC Pending DTC Freeze Frame
P0128 Cooling System Malfunction      

DTC (PGM-FI)

  1. Radiator fan control command check

    -1. Turn the vehicle to the ON mode.

    -2. Clear the DTC with the HDS.

    -3. Turn the blower switch off.

    -4. Check the parameter(s) below with the HDS.

    Signal Threshold Current conditions
    Values Unit Values Unit
    RADIATOR FAN CONTROL About 0 %    

    Do the current condition(s) match the threshold?

    YES 

    Go to step 2.

    NO 

    Wait until the FAN HIGH CTRL and the FAN LOW CTRL are off, then go to step 2.

  2. Radiator fan operation check

    -1. Check the radiator fan operation.

    Does the radiator fan keep running?

    YES 

    Go to step 3.

    NO 

    Go to step 4.

  3. Radiator fan circuit and radiator fan relay check

    -1. Check the radiator fan circuit and the radiator fan relay.

    Is it OK?

    YES 

    Update the PCM if it does not have the latest software, or substitute a known-good PCM , then do the repair verification.

    NO 

    Repair the radiator fan circuit, and the radiator fan relay, then do the repair verification.

  4. Problem verification

    -1. Let the engine cool until the coolant temperature is 104 deg.F (40 deg.C) or less.

    -2. Note the value of ECT SENSOR 1 and ECT SENSOR 2 in the DATA LIST with the HDS.

    Signal Current conditions
    Values Unit
    ECT SENSOR 1    
    ECT SENSOR 2    

    -3. Start the engine, and let it idle.

    -4. Let the engine idle until ECT SENSOR 1 goes up 40 deg.F (22 deg.C) or more from the recorded start temperature.

    Signal Current conditions
    Values Unit
    ECT SENSOR 1    

    -5. Check ECT SENSOR 2 in the DATA LIST with the HDS.

    Signal Current conditions
    Values Unit
    ECT SENSOR 2    

    -6. Compare the recorded start value of ECT SENSOR 2 and the present value of ECT SENSOR 2.

    Did the temperature rise 13 deg.F (7 deg.C) or more?

    YES 

    Test the thermostat and replace it if needed, then do the repair verification.

    NO 

    Intermittent failure, the system is OK at this time. Check for poor connections or loose terminals at ECT sensor 1, ECT sensor 2, and the PCM.

  5. Repair verification (OBD STATUS check)

    -1. Turn the vehicle to the ON mode.

    -2. Reset the PCM with the HDS .

    Reset PCM

    -3. Do the PCM idle learn procedure .

    -4. Let the engine cool until the coolant temperature is between 21 deg.F (-6 deg.C) and 104 deg.F (40 deg.C).

    -5. Test-drive at a steady speed between 15-75 mph (25-120 km/h) for 10 minutes.

    -6. Monitor the OBD STATUS for DTC P0128 in the DTCs MENU with the HDS.

    DTC Description OBD STATUS
    P0128 Cooling System Malfunction  

    DTC (PGM-FI)

    Does the HDS indicate PASSED, FAILED, or NOT COMPLETED?

    PASSED

    Troubleshooting is complete. If the PCM was substituted, replace the original PCM . If any other Pending or Confirmed DTCs are indicated, go to the indicated DTC's troubleshooting.

    FAILED

    Go to step 1 and recheck. If the PCM was updated, substitute a known-good PCM , then check the OBD STATUS again.

    NOT COMPLETED

    Meet the test conditions, and check the OBD STATUS again.

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