DTC P0128

DTC P0128  : Cooling System Malfunction

NOTE:  Before you troubleshoot, review the general troubleshooting information - Refer to: How to Troubleshoot the Fuel and Emissions Systems

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
   FAN HIGH CTRL	OFF
   FAN LOW CTRL	OFF

   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 

   Check for any authorized service information related to the DTCs or symptoms you are troubleshooting or substitute a known-good PCM - Refer to: PCM Removal and Installation (6-Speed A/T), (9-Speed A/T 2016 2017 2018), or PCM Removal and Installation (9-Speed A/T 2019 2020 2021) .

   NO 

   Repair the radiator fan circuit, and the radiator fan relay.

4. Problem verification

   -1. Let the engine cool until the coolant temperature is 104 °F (40 °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 34 °F (19 °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 11 °F (6 °C) or more?

   YES 

   Test the thermostat and replace it if needed .

   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. If the freeze data/on-board snapshot of this DTC is recorded, try to reproduce the failure under the same conditions with the freeze data/on-board snapshot - Refer to: How to Troubleshoot the Fuel and Emissions Systems