Note. Before you troubleshoot, record all freeze data and any on-board snapshot, and review the general troubleshooting information (see GENERAL TROUBLESHOOTING INFORMATION ).
- Turn the ignition switch to ON (II).
- Clear the DTC with the HDS.
- Make sure the blower switch is 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 5.
- Check the radiator fan operation. Does the radiator fan keep running? YES -Check the radiator fan circuit (see «RADIATOR FAN CIRCUIT TROUBLESHOOTING»(ref-290845-S02720214812008072200000) ), and the radiator fan relay (see «POWER RELAY TEST»(ref-290831-S29773354882008072200000) ). If the circuit and the relay are OK, go to step 19 . NO -Go to step 6.
- Let the engine cool until the coolant temperature is 104 T (40
- 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 41°F (231) 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 14°F (8°C) or more from the ambient temperature? YES -Test the thermostat (see «THERMOSTAT TEST»(ref-290817-S09372920842008072200000) ), then go to step 12. 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 ECM/PCM.
- Turn the ignition switch to ON (II).
- Reset the ECM/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 ECM/PCM idle learn procedure (see «ECM/PCM IDLE LEARN PROCEDURE»(ref-290807-S02808252682008072200000) ).
- Test-drive at a steady speed between 15-75 mph (24-120 km/h) for 30 minutes.
- Check for Temporary DTCs or DTCs with the HDS. Is DTC P0128 indicated? YES -Check the cooling system (see «COMPONENT LOCATION INDEX»(ref-290817-S27523063902008072200000) ), 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 (see «COMPONENT LOCATION INDEX»(ref-290817-S27523063902008072200000) ), 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 «ECM/PCM UPDATE»(ref-355245-S27182940282010012100000) ), or substitute a known-good ECM/PCM (see «SUBSTITUTING THE ECM/PCM»(ref-290833-S34742010492008072200000) ).
- 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 (A/T in P or N, M/T in 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 30 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»(ref-290833-S34742010492008072200000) ), 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»(ref-355245-S09328189752010012100000) ). 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»(ref-290833-S34742010492008072200000) ), 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 .