Symptoms

- Engine Light ON (or Service Engine Soon Warning Light)

Possible Causes

- Insufficient warm up time - Low engine coolant level - Leaking or stuck open thermostat - Engine coolant temperature sensor harness is open or shorted - Engine coolant temperature sensor circuit poor electrical connection - Faulty engine coolant temperature sensor

When Detected

The engine coolant temperature does not reach to specified temperature even though the engine has run long enough.

Tech Notes

There is a service bulletin for the following Mazda models: 2004-2005 Mazda3 vehicles 2006-2007 Mazda5 vehicles Mazda Service Bulletin Code P0128

Description

Indicates that the thermostat monitor has not achieved the required engine operating temperature within a specified amount of time after starting the engine.