DTC P0128: Cooling System Malfunction
- Turn the ignition switch ON (II).
- Clear the DTC with the HDS.
- Turn the blower switch OFF.
- Check the FAN CTRL in the DATA LIST with the HDS.
Is it OFF?
YES -Go to step 5.
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 radiator fan circuit (see CIRCUIT DIAGRAM ), and the radiator fan relay (see POWER RELAY TEST ). If the circuits and the relay is OK, go to step 19.
NO -Go to step 6.
- Let the engine cool until the coolant temperature is 40°C (104°F) 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 22°C (40°F) or more from the recorded temperature.
- Check ECT SENSOR 2 in the DATA LIST with the HDS.
- Compare the value of recorded ECT SENSOR 2 and the present value of ECT SENSOR 2.
Did temperature rise 8°C (14°F) 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 ECM/PCM.
NO -Test the thermostat (see FAN MOTOR TEST ), then go to step 12.
- Turn the ignition switch ON (II).
- Reset the ECM/PCM with the HDS.
- Let the engine cool until the coolant temperature is between -6°C (21°F) and 40°C (104°F).
- Do the ECM/PCM idle learn procedure (see ECM/PCM IDLE LEARN PROCEDURE ).
- Test-drive at a steady speed between 24-120 km/h (15-75 mph) for 10 minutes.
- Check for Temporary DTCs or DTCs with the HDS.
Is DTC P0128 indicated?
YES -Check the cooling system, then go to step 1.
NO -Go to step 18.
- 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 17, go to the INDICATED DTCS TROUBLESHOOTING .
NO -If the screen indicates FAILED, check the cooling system, then go to step 1. If the screen indicates NOT COMPLETED, go to step 14.
- Update the ECM/PCM if it does not have the latest software (see UPDATING THE ECM/PCM ), or substitute a known-good ECM/PCM (see SUBSTITUTING THE ECM/PCM ).
- Let the engine cool until the coolant temperature is between -6°C (21°F) and 40°C (104°F).
- Start the engine. Hold the engine speed at 3,000 rpm (min-1 ) without load (in Park or neutral) until the radiator fan comes on, then let it idle.
- Test-drive at a steady speed between 24-120 km/h (15-75 mph) 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 ECM/PCM. If the ECM/PCM was updated, substitute a known-good ECM/PCM (see SUBSTITUTING THE ECM/PCM ), then go to step 20. If the ECM/PCM was substituted, go to step 1.
NO -Go to step 24.
- Monitor the OBD STATUS for DTC P0128 in the DTCs MENU with the HDS.
Does the screen indicate PASSED?
YES -If the ECM/PCM was updated, troubleshooting is complete. If the ECM/PCM was substituted, replace the original ECM/PCM (see ECM/PCM REPLACEMENT ). If any other Temporary DTCs or DTCs were indicated in step 23, 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 ECM/PCM. If the ECM/PCM was updated, substitute a known-good ECM/PCM (see SUBSTITUTING THE ECM/PCM ), then go to step 20. If the ECM/PCM was substituted, go to step 1. If the screen indicates NOT COMPLETED, go to step 20.