Test Description

The numbers below refer to the step numbers on the diagnostic table.

1. 1:  The Diagnostic System Check - Vehicle prompts the technician to complete some basic checks and store the Freeze Frame data on the scan tool if applicable. This creates an electronic copy of the data taken when the fault occurred. The information is then stored in the scan tool for later reference.
2. 2:  This step compares the ECT temperature to the IAT temperature. This inspection is to be performed when the vehicle has reached ambient room temperature. At that time both the surrounding air temperature and the engine coolant temperature are nearly equal. If the ECT sensor and circuit are OK, both sensors should indicate the same temperature.
3. 3:  This step checks that the temperature of the engine coolant increases at least 60°C (140°F) within 20 minutes. If the temperature does not increase to the specified value there is a fault with the ECT sensor or the engine cooling system.
4. 4:  This step checks for a correctly operating engine cooling fan. A cooling fan that comes ON too soon or stays ON all the time, can cause a DTC P0128 to set.
5. 5:  Fault not present indicates the condition that caused DTC P0128 to set is intermittent and not currently present. If no other DTCs are stored, refer to Diagnostic Aids for additional information on diagnosing an intermittent DTC P0128.
6. 16:  After replacing the PCM the relationship between the CKP sensor and the crankshaft must re-established. A new minimum throttle position and idle speed must also be established.