Resistance Inspection

Drain the engine coolant. (See COOLING SYSTEM SERVICE WARNINGS .) (See ENGINE COOLANT REPLACEMENT .)
Remove the ECT sensor.
Place the ECT sensor in water with a thermometer, and heat the water gradually.
Measure the resistance between the ECT sensor terminals using an ohmmeter.

Fig 1: Inspecting Resistance Of Engine Coolant Temperature (ECT) Sensor
Courtesy of MAZDA MOTORS CORP.
- If not as specified, replace the ECT sensor.
- If the ECT sensor is okay, but PID value or PCM terminal 38 voltage are out of specification, perform Circuit Open/Short Inspection .
  Specification
  
  Fig 2: Specification Table
  Courtesy of MAZDA MOTORS CORP.
  
  Fig 3: ECT Sensor Temperature/Resistance Graph
  Courtesy of MAZDA MOTORS CORP.