Test Description

The numbers below refer to the step numbers in the diagnostic procedures.

1. 1  - The Diagnostic System Check - Engine Controls prompts the technician to complete some basic checks and store freeze frame data on the scan tool if applicable. This creates an electronic copy of data taken when fault occurred. Information is then stored in scan tool for later reference.
2. 2  - This step compares the ECT temperature to IAT temperature. This inspection is to be performed when vehicle has reached ambient room temperature. At that time both surrounding air temperature and engine coolant temperature are nearly equal. If ECT sensor and circuit are OK, both sensors should indicate the same temperature.
3. 3  - This step checks temperature of engine coolant increases at least 36°F (20°C) within 10 minutes. If temperature does not increase at least 38°F (20°C) there is a fault with ECT sensor or engine cooling system.
4. 6  - 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.