Diagnostic Aids
WARNING: This page is about a different car, the 2002 Pontiac Grand Am, 2002 Oldsmobile Alero, 2002 Chevrolet Monte Carlo, and 2002 Chevrolet Impala. However, it is still accessible from the selected car via links, so may be relevant.
- DTC P0128 is designed to detect a faulty thermostat.
- A skewed ECT sensor may cause a DTC P0128 to set.
- If a DTC P0125 and P0128 are both set, a skewed ECT sensor is the most likely cause.
- A skewed Intake Air Temperature (IAT) sensor may cause this DTC to set.