18-016-13

This bulletin involves reprogramming the Powertrain Control Module with new software. The Technician may discover that P0128 - Thermostat Rationality DTC is present. This DTC is a two trip code and is matured if a significant difference exists between the PCM predicted and actual engine coolant temperature during engine warm-ups. The PCM calibration may improperly mature a P0128 DTC because the airflow across the coolant temperature sensor during colder ambient temperatures, 50° F (10° C) or below, causes the predicted coolant temperature to deviate from the actual coolant temperature.