Diagnostic Test

WARNING: This page is about a different variant/trim than selected.

LOW COOLANT LEVEL
NOTE:
If any ECT, AAT, CMP or CKP Sensor DTCs have set along with P0128, diagnose them before continuing.

NOTE:
Inspect the ECT terminals and related PCM terminals. Make sure the terminals are free from corrosion and damage.

NOTE:
The best way to diagnose this DTC is to allow the vehicle to sit overnight outside in order to have a totally cold soaked engine.

NOTE:
Extremely cold outside ambient temperatures may have caused this DTC to set.

WARNING:
Never open the cooling system when the engine is hot. The system is under pressure. Failure to follow these instructions can result in personal injury including extreme burns, scalding, or fatal injury. Allow the engine to cool before opening the cooling system.
1. Check the cooling system to make sure that the coolant is in good condition and at the proper level. Refer to DIAGNOSIS AND TESTING .
  Is the coolant level and condition OK?
  
  Yes
  - Go To 2
  No
  - Inspect the vehicle for a coolant leak and add the necessary amount of coolant.
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .
AMBIENT AIR TEMP SENSOR OPERATION
1. Turn the ignition on.
2. With the scan tool, read and record the AAT Sensor Temperature value.
3. Monitor the actual ambient air temperature near the AAT Sensor with a thermometer.
  Is the AAT Sensor value within -15°C (5°F) of the thermometer reading?
  
  Yes
  - Go To 3
  No
  - Replace the Ambient Air Temperature Sensor in accordance with the Service Information.
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .
ECT SENSOR OPERATION
WARNING:
Make sure the engine cooling system is cool before removing the pressure cap or any hose. The cooling system is pressurized when hot. Failure to follow these instructions can result in possible serious or fatal injury.
1. With the scan tool, read and record the ECT Sensor Temperature value.
2. Monitor the actual coolant temperature with a thermometer.
  Is the ECT Sensor value with -15°C (5°F) of the thermometer reading?
  
  Yes
  - Go To 4
  No
  - Replace the Engine Coolant Temperature Sensor in accordance with the Service Information.
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .
THERMOSTAT OPERATION
1. Turn the ignition on.
2. With the scan tool, read the ECT Sensor Degree value. If the engine was allowed to sit overnight (cold soak), the temperature value should be a value that is somewhere close to the ambient temperature.
  NOTE:
  If engine coolant temperature is above 82°C (180°F), allow the engine to cool until 65°C (150°F) is reached.
3. Start the Engine.
4. During engine warm-up, monitor the ECT Sensor Degree value. The temp degree value change should be a smooth transition from start up to normal operating temp 82°C (180°F). Also monitor the actual coolant temperature with a thermometer.
  NOTE:
  As the engine warms up to operating temperature, the actual coolant temperature (thermometer reading) and the scan tool, ECT Temperature value should stay relatively close to each other.
5. Using the appropriate Service Information, determine the proper opening temperature of the thermostat.
  Did the thermostat open at the proper temperature?
  
  Yes
  - Go To 5
  No
  - Replace the thermostat in accordance with the Service Information. Refer to THERMOSTAT, REMOVAL .
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .
OTHER POSSIBLE CAUSES
1. Perform any Service Bulletins (Service Bulletins) that may apply.
2. Inspect the Temperature Sensors for any physical damage.
3. Inspect the engine coolant. Make sure the coolant is at the proper level.
4. Make sure the Temperature Sensors are properly installed.
5. Make sure the CMP and CKP sensors are installed properly. Check the connectors for any signs of damage.
6. With the engine running at normal operating temperature, monitor the Temperature sensor parameters while wiggling the wire harness. Look for parameter values to change.
7. Visually inspect the related wire harness. Look for any chafed, pierced, pinched, partially broken wires and broken, bent, pushed out or corroded terminals.
8. Inspect and clean all PCM, engine and chassis grounds.
  Were any problems found during the above inspections?
  
  Yes
  - Repair as necessary.
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .
  No
  - Go To 6
POWERTRAIN CONTROL MODULE (PCM)
1. Using the wiring diagram/schematic as a guide, inspect the wiring and connectors between the Temperature Sensors and the Powertrain Control Module (PCM).
2. Look for any chafed, pierced, pinched or partially broken wires.
3. Look for broken, bent, pushed out or corroded terminals. Verify that there is good pin to terminal contact in the Sensor and Powertrain Control Module connectors.
4. Perform any Service Bulletins that may apply.
  Were there any problems found?
  
  Yes
  - Repair as necessary.
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .
  No
  - Replace and program the Powertrain Control Module in accordance with the Service Information. Refer to MODULE, POWERTRAIN CONTROL (PCM), REMOVAL .
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .