Coolant Temperature Sensor/Switch (For Computer): Testing and Inspection

Engine Coolant Temperature Sensor, Checking

CAUTION!
• Cooling system is under pressure.

• Danger of scalding when opening!

• Use only gold-plated terminals when servicing terminals in the electrical harness connector of Engine Coolant Temperature (ECT) Sensor (G62).

Special tools, testers and auxiliary items required

• Multimeter.

• jumper wire.

• Wiring diagram.

Test requirements

• The Diesel Direct Fuel Injection (DFI) Engine Control Module (ECM) (J248) 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 (GND) connections between engine/transmission/chassis OK.

• Ignition switched off.

• Engine cold.

Test procedure

- Perform a preliminary check to verify the customers complaint. Refer to => [ Preliminary Check ] Preliminary Check.

Start diagnosis

- Perform the function test in diagnostic mode 06. Refer to => [ Diagnostic Mode 06 - Read Test Results for Specific Diagnostic Functions ] Diagnostic Mode 06 - Read Test Results For Specific Diagnostic Functions.

If the specified values were not obtained:

Checking internal resistance

- Disconnect the Engine Coolant Temperature (ECT) Sensor (G62) electrical harness connector - 1 -.





- Using a multimeter, check the Engine Coolant Temperature (ECT) Sensor (G62) terminals 1 to 3 for resistance.

Use the chart below for the specified values:





• Area A: Resistance values 0 to 50° C (32° - 122° F).

• Area B: Resistance values 50 to 100° C (122° - 212° F).

Examples:

• Range A, 30° C (86° F) equals a resistance of 1500 to 2000 ohms

• Range B, 80° C (176° F) equals a resistance of 275 to 375ohms

If any of the specified values were not obtained:

- Replace the Engine Coolant Temperature (ECT) Sensor ( G62).

If the specified values were obtained:

Checking wiring

If the manufacturers test box is being used, perform the following step.

- Install the test box. Refer to => [ 68 Pin Test Box Adapter, Installing ] 68 Pin Test Box Adapter, Installing.

If the manufacturers test box is not being used, perform the following step.

- Remove the Diesel Direct Fuel Injection (DFI) Engine Control Module (ECM) (J248). Refer to => [ Engine Control Module, Replacing ] Engine Control Module, Replacing.

- Using a Multimeter, check the Engine Coolant Temperature (ECT) Sensor ( G62) electrical harness connector terminals to the Diesel Direct Fuel Injection (DFI) Engine Control Module (ECM) (J248) electrical harness connector T60 terminals for resistance.









Specified value: 1.5 ohms Max.

If the specification was not obtained:

- Check the wiring for a short circuit to each other, Battery (+), and Ground (GND).

- Check the electrical harness connector for damage, corrosion, loose or broken terminals.

- If necessary, repair the faulty wiring connection.

If no malfunction is detected in the wiring:

- Erase the DTC memory. Refer to => [ Diagnostic Mode 04 - Erase DTC Memory ] Diagnostic Mode 04 - Erase DTC Memory.

- Perform a road test to verify repair.

If the DTC does not return:

Repair complete, Generate readiness code. Refer to => [ Readiness Code ] Readiness Code.

- End diagnosis.

If the DTC does return and no malfunction is detected in the wiring and the voltage supply was not OK:

- Replace the Diesel Direct Fuel Injection (DFI) Engine Control Module (ECM) (J248). Refer to => [ Engine Control Module, Replacing ] Engine Control Module, Replacing.

- Assembly is performed in the reverse of the removal.

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 Mode 03 - Read DTC Memory.

2. If necessary, erase the DTC memory. Refer to => [ Diagnostic Mode 04 - Erase DTC Memory ] Diagnostic Mode 04 - Erase DTC Memory.

3. If the DTC memory was erased, generate readiness code. Refer to => [ Readiness Code ] Readiness Code.

End of diagnosis