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 HIGH CTRL and FAN LOW CTRL in the DATA LIST with the HDS. Is It OFF? YES -Go to step 5. NO -Wait until the FAN HIGH CTRL and FAN LOW 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 HIGH SPEED CIRCUIT TROUBLESHOOTING»(ref-513184-S01663488672012110700000) ) and the radiator fan relay (see «POWER RELAY TEST»(ref-513170-S00592820692012110700000) ). 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°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 is 36°F (20°C).
- 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 13°F (7°C) or more? YES -Test the thermostat (see «FAN MOTOR TEST»(ref-513159-S39880185132012110700000) ), 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 19°F (-7°C) and 124°F (51°C).
- Do the PCM idle learn procedure (see «PCM IDLE LEARN PROCEDURE»(ref-513173-S16164063582012110700000) ).
- Test-drive at a steady speed between 15-75 mph (24-120 km/h) for 10 minutes.
- Check for Pending or Confirmed DTCs with the HDS. Is DTC P0128 indicated? YES -Check the cooling the system, then go to step 19 . 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 or Confirmed DTCs were indicated in step 17 , go to the indicated «DTC'S TROUBLESHOOTING»(ref-513153-S06499438282012110700000) . NO -If the HDS indicates FAILED, check the cooling system (see «COMPONENT LOCATION INDEX»(ref-513159-S01605706512012110700000) ). If the cooling system is OK, 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-513153-S08553155092012110700000) ), or substitute a known-good PCM (see «SUBSTITUTING THE PCM»(ref-513169-S18138486322012110700000) ).
- Let the engine cool until the coolant temperature is between 19°F (-7°C) and 124°F (51°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 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-513169-S18138486322012110700000) ), 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-513153-S08243124262012110700000) ). If any other Pending or Confirmed DTCs were indicated in step 23 , go to the indicated «DTC'S TROUBLESHOOTING»(ref-513153-S06499438282012110700000) . 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-513169-S18138486322012110700000) ), then go to step 20 . If the PCM was substituted, go to step 1 . If the HDS indicates NOT COMPLETED, go to step 20 .