P0128-THERMOSTAT RATIONALITY
For a complete wiring diagram, refer to the wiring information.
* When Monitored: With the engine running, start up coolant temperature between -8°C (17.6°F) and 50°C (122°F), the difference between ambient temperature and coolant temperature less than 10°C (50°F) and average vehicle speed greater than 16 kph (10 mph) for more than 18% of vehicle run time.
* Set Condition: The PCM detects that the actual engine coolant temperature does not reach the predicted engine coolant temperature within a specific time. Two trip fault. Three good trips to turn off the MIL.
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. See: Initial Inspection and Diagnostic Overview Pre-Diagnostic Troubleshooting Procedure
1. CHECKING THE TEMPERATURE SENSORS.
NOTE: Diagnose and repair any ambient air temperature (AAT), intake air temperature (IAT), or engine coolant temperature (ECT) sensor circuit or rationality DTCs before continuing with this test.
NOTE: Diagnose and repair any crankshaft (CKP) or camshaft (CMP) sensor circuit or rationality DTCs before continuing with this test.
NOTE: Diagnose and repair any communication DTCs before continuing with this test.
NOTE: Verify that the Pinion Factor has been programmed correctly into the PCM.
1. Perform the diagnostic procedure for CHECKING THE TEMPERATURE SENSORS. See: Component Tests and General Diagnostics Checking the Temperature Sensors
Were any problems found?
Yes
* Repair as necessary.
* Perform the PCM VERIFICATION TEST. See: Verification Tests PCM Verification Test.
No
* Go To 2
2. CHECKING THE ENGINE COOLANT TEMPERATURE SENSOR OPERATION.
1. Perform the diagnostic procedure for CHECKING THE ENGINE COOLANT TEMPERATURE SENSOR OPERATION. See: Component Tests and General Diagnostics Checking the Engine Coolant Temperature Sensor Operation
Were any problems found?
Yes
* Repair as necessary.
* Perform the PCM VERIFICATION TEST. See: Verification Tests PCM Verification Test.
No
* Refer to the CHECKING FOR AN INTERMITTENT DTC Diagnostic Procedure. See: Initial Inspection and Diagnostic Overview Checking for an Intermittent DTC
Wednesday, March 23rd, 2011 AT 3:21 PM