DTC P0128: Cooling System Malfunction
- Turn the ignition switch ON (II).
- Clear the DTC with the HDS.
- Turn the blower switch OFF.
- Turn the A/C switch OFF.
- Check the FAN CTRL in the DATA LIST with the HDS.
Is it OFF?
YES - Go to step 6.
NO - Wait until the FAN CTRL is off, then go to step 6.
- Check the radiator fan operation.
Does the radiator fan keep running?
YES - Check the cooling system (see RADIATOR CAP TEST ). If the cooling system is OK, go to step 20.
NO - Go to step 7.
- Let the engine cool until the coolant temperature is 104°F(40°C) or less.
- Note the value of ECT SENSOR 1 and ECT SENSOR 2 in the DATA LIST with the HDS.
- Start the engine, and let it idle.
- Let the engine idle until ECT SENSOR 1 goes up 49°F (27°C) or more from the recorded temperature.
- Check ECT SENSOR 2 in the DATA LIST with the HDS.
- Compare the recorded value of ECT SENSOR 2 and the present value of ECT SENSOR 2.
Did temperature rise 17°F (9.5°C) or more?
YES - 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
NO - Test the thermostat (see FAN MOTOR TEST ), then go to step 13.
- Turn the ignition switch ON (II).
- Reset the PCM with the HDS.
- Let the engine cool until the coolant temperature is between 21°F (-6°C) and 104°F (40°C).
- Do the PCM idle learn procedure (see PCM IDLE LEARN PROCEDURE ).
- Test-drive at a steady speed between 15-75 mph (24-120 km/h) for 10 minutes.
- Check for Temporary DTCs or DTCs with the HDS.
Is DTC P0128 indicated?
YES - Check for poor connections or loose terminals at ECT sensor 1, ECT sensor 2, and the PCM. then go to step 1.
NO - Go to step 19.
- Monitor the OBD STATUS for DTC P0128 in the DTCs MENU with the HDS.
Does the screen indicate PASSED?
YES - Troubleshooting is complete. If any other Temporary DTCs or DTCs were indicated in step 18, go to the indicated DTCs troubleshooting
NO - If the screen indicates FAILED, check for poor connections or loose terminals at ECT sensor 1, ECT sensor 2, and the PCM, then go to step 1. If the screen indicates NOT COMPLETED, go to step 17.
- Update the PCM if it does not have the latest software (see UPDATING THE PCM ), or substitute a known-good PCM (see SUBSTITUTING THE PCM ).
- Let the engine cool until the coolant temperature is between 21°F (-6°C) and 104°F (40°C).
- Start the engine. Hold the engine speed at 3,000 RPM without load (in Park or neutral) until the radiator fan comes on, then let it idle.
- Test-drive at a steady speed between 15-75 mph (24-120 km/h) for 10 minutes.
- Check for Temporary DTCs or DTCs with the HDS.
Is DTC P0128 indicated?
YES - Check for poor connections or loose terminals at ECT sensor 1, ECT sensor 2, and the PCM. If the PCM was updated, substitute a known-good PCM (see SUBSTITUTING THE PCM ), then go to step 21. If the PCM was substituted, go to step 1.
NO - Go to step 25.
- Monitor the OBD STATUS for DTC P0128 in the DTCs MENU with the HDS.
Does the screen indicate PASSED?
YES - If the PCM was updated, troubleshooting is complete. If the PCM was substituted, replace the original PCM (see PCM REPLACEMENT ). If any other Temporary DTCs or DTCs were indicated in step 24, go to the indicated DTCs troubleshooting
NO - If the screen indicates FAILED, check for poor connections or loose terminals at ECT sensor 1, ECT sensor 2, and the PCM. If the PCM was updated, substitute a known-good PCM (see SUBSTITUTING THE PCM ), then go to step 21. If the PCM was substituted, go to step 1. If the screen indicates NOT COMPLETED, go to step 21.