Diagnostic Aids
WARNING: This page is about a different car, the 2003 GMC Sierra, 2003 GMC Cab & Chassis Sierra, 2003 Chevrolet Silverado, and 2003 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.
- A DTC P0128 is designed to detect a faulty thermostat.
- A skewed ECT sensor may cause a P0128 to set.
- This DTC will not run if either the intake air or coolant temperature is too low at start-up.
- If an intermittent condition exists, see INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM.
- Using Freeze Frame/Failure Records may aid in determining the conditions under which the failure occurred.