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 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 radiator fan high speed circuit (see «RADIATOR FAN HIGH SPEED CIRCUIT TROUBLESHOOTING»(ref-243328-S37832254872006082300000) ). If the circuits and the relay 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 40°F (22°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 «THERMOSTAT TEST»(ref-243298-S00608961722006082300000) ), 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»(ref-243313-S13405059332006082300000) ).
- 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 the cooling system, 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 DTC's 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 15 .
- Update the PCM if it does not have the latest software (see «UPDATING THE PCM»(ref-243311-S19790429062006082300000) ), or substitute a known-good PCM (see «HOW TO SUBSTITUTE THE PCM»(ref-243311-S24543735662006082300000) ).
- 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 «HOW TO SUBSTITUTE THE PCM»(ref-243311-S24543735662006082300000) ), 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»(ref-298125-S08727755362008091500000) ). If any other Temporary DTCs or DTCs were indicated in step 24 , go to the indicated DTC's 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 «HOW TO SUBSTITUTE THE PCM»(ref-243311-S24543735662006082300000) ), then go to step 21 . If the PCM was substituted, go to step 1 . If the screen indicates NOT COMPLETED, go to step 21 .