Engine Coolant Temperature Gauge Test

Fig 1: Testing Engine Coolant Temperature Gauge

Courtesy of MAZDA MOTORS CORP.

1. Disconnect ECT sender connector. Connect one lead of Fuel Thermometer SST  49 0839 285 to the sender connector (R/W) and the other lead to ground.
2. Set Fuel Thermometer SST 49 0839 285  to 300 ohms. Key ON. Wait one minute. The engine coolant temperature gauge should indicate C (cold). Key OFF.
3. Set Fuel Thermometer SST 49 0839 285  to 45 ohms. Key ON. Wait one minute. The engine coolant temperature gauge pointer should be in the one quarter range to mid range. Key OFF.
4. Set Fuel Thermometer SST 49 0839 285  to 18 ohms. Key ON. Wait one minute. The engine coolant temperature gauge should indicate H (hot). Key OFF. Return to TEMPERATURE GAUGE INDICATION INCORRECT .