P0128 Fault in 2005 Chevrolet TrailBlazer: Engine Not Warming Up and Transmission Fluid Burning
Hi everyone, I'm experiencing a persistent issue with my 2005 Chevrolet TrailBlazer. The engine is showing fault code P0128 — 'Engine Coolant Temperature Below Thermostat Regulation Temperature'. My mechanic confirmed this code after diagnosing the problem. The transmission fluid is burning and changing color over time, with a strong burnt smell. Despite no dashboard warning lights, I've noticed a clear deterioration in fluid condition day by day. I recently replaced the radiator and checked the cooling fan — both are functioning properly. However, the engine still isn
P0128 relates to the engine not warming up properly, not the transmission. I recommend using an OBD2 scanner to check the Engine Coolant Temperature (ECT) sensor reading. A faulty ECT sensor or a defective thermostat could be causing this issue. It's also possible that during radiator replacement, a coolant line was damaged or collapsed — check for leaks or restricted flow by visually inspecting lines or performing a pressure test. As a last resort, consider replacing the transmission fluid filter and flushing the cooling system to ensure no blockages exist in the coolant lines.