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; '09-11 models (see «2009-2011 MODELS»(ref-336484-S40502600682012012400000) ), '12 model (see «2012 MODEL»(ref-336484-S19432386032012012400000) ),and the radiator fan relay (see «POWER RELAY TEST»(ref-336471-S28167947572009072700000) ). If the system and the relay are OK, Go to step 19 . NO -Go to step 6.
- 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 -Test the thermostat (see «THERMOSTAT TEST»(ref-336459-S41880014302009072700000) ), 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 PCM.
- Turn the ignition switch to 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»(ref-336473-S09468920992009072700000) ).
- Test-drive at a steady speed between 15-75 mph (24-120 km/h) for 30 minutes.
- Check for Pending DTCs or Confirmed 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 18.
- Monitor the OBD STATUS for DTC P0128 in the DTCs MENU with the HDS. Does the HDS indicate PASSED? YES -Troubleshooting is complete. If any other Pending DTCs or Confirmed DTCs were indicated in step 17, Go to the indicated DTC's troubleshooting. • NO -If the HDS indicates FAILED, check the cooling system, then go to step 19. If the HDS indicates NOT COMPLETED, go to step 14 .
- Update the PCM if it does not have the latest software (see «PCM UPDATE»(ref-336453-S09500398002009072700000) ), or substitute a known-good PCM (see «SUBSTITUTING THE PCM»(ref-336452-S17145915352009072700000) ).
- 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 P or N) 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 Pending DTCs or Confirmed 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»(ref-336452-S17145915352009072700000) ), then Go to step 20 . If the 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 HDS indicate PASSED? YES -If the PCM was updated, troubleshooting is complete. If the PCM was substituted, replace the original PCM (see «PCM REPLACEMENT»(ref-336453-S28620960052009072700000) ). If any other Pending DTCs or Confirmed DTCs were indicated in step 23, Go to the indicated DTC's troubleshooting. • NO -If the HDS 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»(ref-336452-S17145915352009072700000) ), then Go to step 20 . If the PCM was substituted, Go to step 1 . If the HDS indicates NOT COMPLETED, Go to step 20.