The P0128 trouble code indicates that the engine’s coolant temperature is below the thermostat regulating temperature. This code typically points to issues related to the functionality of the engine’s thermostat, leading to improper regulation of the engine’s operating temperature.
Coolant Thermostat (Coolant Temperature Below Thermostat Regulating Temperature)
Code symptoms P0128.
1. Slow engine warm-up.
2. Decreased fuel efficiency.
3. Malfunction indicator light (MIL) illumination.
This code is common in brands such as:: Chevrolet, Renault, Ford, Toyota, Nissan, Mercedes Benz, Honda.
Causes of the code P0128.
1. Stuck open thermostat.
2. Low engine coolant level.
3. Problems with the Engine Control Module (ECM).
Code Solutions P0128.
1. Replace the thermostat if it is stuck open.
2. Check and refill the engine coolant to the appropriate level.
3. If ECM issues are suspected, consult a qualified technician for diagnosis and potential reprogramming or replacement.