DTC P0126 & P0128: Coolant Thermostat Stuck Open: Notes

WARNING: This page is about a different car, the 2004 Mazda 6. However, it is still accessible from the selected car via links, so may be relevant.

Fig 1: DTC P0126 & P0128 - Detection Conditions & Possible Causes

Courtesy of MAZDA MOTORS CORP.