P0128 – Troubleshooting Engine Coolant Temperature Below Thermostat Regulating Temperature The issue with that tactic is that the check engine light is capable of informing you that there is a problem – it doesn’t tell you how many faults the ECM/PCM has identified – unless there’s an actual one. For more information click on link - https://oemusedcarpart.com/car-engine/p0128/