Engine Coolant Temperature Sensor Operation Test

Engine Coolant Temperature Sensor Operation Test

For a complete wiring diagram, refer to.

Test Step 1 - ECT Sensor Wiring and Connectors

• Diagnose and resolve any ECT circuit DTCs before proceeding with this test.

• Allow the engine to cool to ambient temperature before proceeding.

• Using the wiring diagram/schematic as a guide, inspect the wiring and connectors between the ECT sensor and the PCM.

• Look for any chafed, pierced, pinched, or partially broken wires.

• Look for broken, bent, pushed out or corroded terminals.

• Turn the ignition on.

• Monitor the scan tool data relative to the sensor and wiggle test the wiring and connectors.

• Look for the data to change or for a DTC to set during the wiggle test.

Were any problems found?

Yes

• Repair as necessary.

• Perform the PCM Verification Test. Refer to => [ PCM Verification Test ] PCM Verification Test.

No

• Go to Test Step 2

Test Step 2 - Engine Coolant Level and Condition

Make sure the engine cooling system is cool before removing the pressure cap or any hose. The cooling system is pressurized when hot. Failure to follow these instructions can result in personal injury including extreme burns, scalding, or fatal injury.

• Check the engine coolant level and the condition of the engine coolant.

Were any problems found?

Yes

• Repair as necessary.

• Perform the PCM Verification Test. Refer to => [ PCM Verification Test ] PCM Verification Test.

No

• Go to Test Step 3

Test Step 3 - Thermostat

Make sure the engine cooling system is cool before removing the pressure cap or any hose. The cooling system is pressurized when hot. Failure to follow these instructions can result in personal injury including extreme burns, scalding, or death.

• Using the appropriate service information, determine the proper opening temperature of the thermostat.

• With the scan tool, read the engine coolant temperature sensor value. If the engine was allowed to cool completely, the value should be approximately equal to the ambient temperature.

• Monitor the sensor value on the scan tool.

• Start the engine.

When the engine is operating, do not stand in direct line with the fan. Do not put your hands near the pulleys, belts, or fan. Do not wear loose clothing. Failure to follow these instructions can result in possible serious or fatal injury.

• The thermostat should not open until the engine reaches the temperature specified in the service information.

Were any problems found?

Yes

• Repair as necessary.

• Perform the PCM Verification Test. Refer to => [ PCM Verification Test ] PCM Verification Test.

No

• Go to Test Step 4

Test Step 4 - Engine Coolant Temperature Sensor

• Allow the engine to cool to ambient temperature before proceeding.

Make sure the engine cooling system is cool before removing the pressure cap or any hose. The cooling system is pressurized when hot. Failure to follow these instructions can result in personal injury including extreme burns, scalding, or death.

• With the scan tool, read the ECT sensor value. If the engine was allowed to cool completely, the value should be approximately equal to the ambient temperature.

• Monitor the sensor value on the scan tool and the actual coolant temperature with a thermometer.

• Start the engine.

When the engine is operating, do not stand in direct line with the fan. Do not put your hands near the pulleys, belts, or fan. Do not wear loose clothing. Failure to follow these instructions can result in personal injury or death.

• The sensor value transition should be smooth as the engine reaches operating temperature. The thermometer reading and the coolant temperature value on the scan tool should remain relatively close.

Were any problems found?

Yes

• Go to Test Step 5

No

• Test complete.

• Perform the PCM Verification Test. Refer to => [ PCM Verification Test ] PCM Verification Test.

Test Step 5 - ECT Signal Circuit High Resistance

• Turn the ignition off.

Do not probe the PCM harness connectors. Probing the PCM harness connectors will damage the PCM terminals resulting in poor terminal to pin connection. Install Miller Special Tool #8815 along with the #8815-1 to perform the diagnosis.

• Using a voltmeter, perform a voltage drop test by backprobing the sensor ground circuit at the ECT sensor harness connector and by probing the appropriate terminal of the special tool #8815. Make sure the voltmeter leads are connected so that positive polarity is displayed on the voltmeter.

When the engine is operating, do not stand in direct line with the fan. Do not put your hands near the pulleys, belts, or fan. Do not wear loose clothing. Failure to follow these instructions can result in personal injury or death.

• Start the engine.

Is the voltage less than 0.5 volts?

Yes

• Go to Test Step 7

No

• Repair the sensor ground circuit for excessive resistance.

• Perform the PCM Verification Test. Refer to => [ PCM Verification Test ] PCM Verification Test.

Test Step 7 - ECT Sensor

• Using the wiring diagram/schematic as a guide, inspect the wiring and connectors between the ECT sensor and the PCM.

• Look for any chafed, pierced, pinched, or partially broken wires.

• Look for broken, bent, pushed out or corroded terminals.

• Refer to any TSBs that may apply.

Were any problems found?

Yes

• Repair as necessary.

• Perform the PCM Verification Test. Refer to => [ PCM Verification Test ] PCM Verification Test.

No

• Replace the ECT sensor.

• Perform the PCM Verification Test. Refer to => [ PCM Verification Test ] PCM Verification Test.