P0126 and P0128 Error Code in 2005 Mazda 3: Is a Stuck Open Thermostat the Cause?
I own a 2005 Mazda 3 with a 2.0-liter engine and have reached 116,000 miles. The check engine light activated, and after scanning the vehicle's OBD-II system, I found two fault codes: P0126 and P0128. After some online research, I suspect that the thermostat may be stuck open, which could be causing these errors. Is this a valid diagnosis? Can anyone confirm or provide guidance on how to resolve this issue? Thank you for your help. Cory
The P0126 and P0-128 codes are commonly reported in various vehicle makes and models, including the 2005 Mazda 3. A stuck-open thermostat is a likely culprit. I recommend replacing it with an OEM or dealer-grade thermostat to ensure proper operating temperature and correct opening point.