Coolant Temperature Sensor/Switch (For Computer): Testing and Inspection
Engine Coolant Temperature Sensor 1 or 2 Checking
• Cooling system is under pressure.
• Danger of scalding when opening!
• . ECT 1 is identified as G62 and is located on the thermostat housing. ECT 2 is identified as G83 and is located on the lower radiator hose. Use only gold-plated terminals when servicing terminals in the electrical harness connector of Engine Coolant Temperature (ECT) Sensor (G62 or G83)
Special tools, testers and auxiliary items required
• Multimeter.
• Jumper wire.
• Wiring diagram.
Test requirements
• The Engine Control Module (ECM) (J623) fuses OK.
• Battery voltage at least 12.5 volts.
• All electrical consumers such as, lights and rear window defroster, switched off.
• Vehicles with automatic transmission, shift selector lever into position "P" or "N".
• A/C switched off.
• Ground connections between engine/transmission/chassis OK.
• Ignition switched OFF.
• Engine should be cold to verify low temperature readings and monitor increase while engine is running.
Test procedure
- Perform a preliminary check to verify the customers complaint. Refer to => [ Preliminary Check ] Preliminary Check
Start diagnosis
- Connect the scan tool.
- Switch the ignition ON.
- Using the scan tool, check the coolant temperature:
If reading is out of range, continue test according to the following table:
If the specified value was obtained:
- Start the engine and let it run at idle.
The temperature value must increase uniformly in increments of 1.0 °C.
- Turn the ignition switch OFF
If the engine shows problems in certain temperature ranges and if the temperature does not climb uniformly or the temperature signal is intermittent.
- Replace the the Engine Coolant Temperature (ECT) Sensor (G62 or 83) Refer to the Repair Information.
Checking internal resistance
- Disconnect the the Engine Coolant Temperature (ECT) Sensor (G62 or 83) electrical harness connector.
- Using a multimeter, check the the Engine Coolant Temperature (ECT) Sensor (G62 or 83) terminals 1 to 2 for resistance.
Use the chart below for the specified values:
Specified values:
If the specified values were Not obtained:
- Replace the the Engine Coolant Temperature (ECT) Sensor (G62 or 83) Refer to the Repair Information.
°Testing if display is approx. - 40.0 C
- Disconnect the the Engine Coolant Temperature (ECT) Sensor (G62 or 83) electrical harness connector.
- Using a jumper wire, connect the the Engine Coolant Temperature (ECT) Sensor (G62 or 83) electrical harness connector terminals 1 to 2.
- Turn the ignition switch ON
- Check the value indicated on the scan tool display.
- Turn the ignition switch OFF
If the value jumps to approx. 140.0° C
- Replace the the Engine Coolant Temperature (ECT) Sensor (G62 or 83) Refer to the Repair Information.
If indication remains at approx. - 40.0° C:
Checking wiring
- Remove the Engine Control Module (ECM) (J623). Refer to the Repair Information.
- Using a multimeter, check the the Engine Coolant Temperature (ECT) Sensor (G62 or 83) electrical harness connector terminals to the Engine Control Module (ECM) (J623) electrical harness connector T60 terminals for an open circuit or a short to voltage, refer to the chart below.
OR
Specified values: 1.5 ohms Max. and 0 volts with key on and ECM disconnected.
If the specified value was Not obtained:
- Check the wiring for an open or short circuit to Battery (+).
- Check the electrical harness connector for damage, corrosion, loose or broken terminals.
- If necessary, repair the faulty wiring connection.
If the specified value was obtained:
- Using a multimeter, check terminal 2 of the ECT sensor to engine ground.
Specified value: 1.5 ohms Max
If the specified value was Not obtained:
- Check the wiring for an open circuit or high resistance.
- Check the electrical harness connector for damage, corrosion, loose or broken terminals.
- If necessary, repair the faulty wiring connection.
If the specified value was obtained:
- Replace the Engine Control Module (ECM) (J623). Refer to the Repair Information.
°Testing if display approx. 140.0 C
- Disconnect the the Engine Coolant Temperature (ECT) Sensor (G62 or 83) electrical harness connector.
- Turn the ignition switch ON.
If indication jumps to approx. - 40.0 °C:
- Switch ignition OFF.
- Replace the Engine Coolant Temperature (ECT) Sensor (G62 or 83) Refer to the Repair Information.
If the value remains at approx. 140.0 °C
Checking wiring
- Remove the Engine Control Module (ECM) (J623) and disconnect the ECM connectors. Refer to the Repair Information.
- Disconnect the ECT harness connector at the sensor.
- Using a multimeter, check the signal circuit of the the Engine Coolant Temperature (ECT) Sensor (G62 or 83) electrical harness connector terminal 1 to engine ground.
Specified value: OL or no continuity.
If the specified value was Not obtained:
- Check the wiring for a short circuit to Ground.
- Check the electrical harness connector for damage, corrosion, loose or broken terminals.
- If necessary, repair the faulty wiring connection.
If the specified value was obtained:
- Replace the Engine Control Module (ECM) (J623). Refer to the Repair Information.
Final procedures
After the repair work, the following work steps must be performed in the following sequence:
1. Check the DTC memory. Refer to => [ Diagnostic Mode 03 - Read DTC Memory ] Diagnostic Modes 01 - 09.
2. If necessary, erase the DTC memory. Refer to => [ Diagnostic Mode 04 - Erase DTC Memory ] Diagnostic Modes 01 - 09.
3. If the DTC memory was erased, generate readiness code. Refer to => [ Readiness Code ] Monitors, Trips, Drive Cycles and Readiness Codes.