Diagnostic Aids

If the engine is allowed to cool overnight, the coolant temperature sensor and MAT sensor should read close to each other, when measured with a "Scan" tester. A Code 25 will also result if sensor signal circuit is shorted to ground.

Fig 1: Code 25, MAT Sensor Temp Hi Ckt Diag

Fig 2: Code 25, MAT Sensor Temp Hi Flow Chart