Engine Coolant Temperature Sensor, Checking

Engine Coolant Temperature Sensor, Checking

Observe all safety precautions: => [ Safety Precautions ] Generic Scan Tool

View clean working conditions: => [ Clean Working Conditions ] Clean Working Conditions

Prior to repair work, perform a preliminary check to verify the condition. Refer to => [ Preliminary Check ] Preliminary Check.

Use only gold-plated terminals when servicing any component with gold-plated electrical harness connector terminals.

For wiring diagrams, component locations, and connector views, refer to the applicable wiring diagram.

Special tools, testers and auxiliary items required

• Generic scan tool

• Multimeter

• Wiring diagram

Test requirements

• The Motronic 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 (GND) connections between engine/transmission/chassis OK.

• Ignition switched off.

• Engine cold.

Test procedure

Start diagnosis

- Connect the scan tool.

- Switch the ignition on.

- Using the scan tool, check the coolant temperature:

If the specified value was not obtained:

- Continue test according to the following table:

If the specified value was obtained:

Checking internal resistance

- Disconnect the Engine coolant temperature sensor (G62) electrical harness connector - 1 -.

- Using a Multimeter , check the Engine coolant temperature sensor (G62) terminals 1 to 2 for resistance.

Use the chart below for the specified values:

Specified values:

If any of the specified value's were not obtained:

- Replace the Engine coolant temperature sensor (G62). Refer to appropriate service manual.

- Go to Final procedures

If the specified value was obtained:

- Replace the Motronic Engine Control Module (ECM) (J623). Refer to appropriate service manual.

- Go to Final procedures

°Testing if scan tool display is approximately - 40.0 C

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

- Using a jumper wire, connect the Engine Coolant Temperature (ECT) Sensor (G62) electrical harness connector terminals 1 to 2.

- Switch the ignition on.

- Check the value indicated on the scan tool display.

Specified value: scan tool display approximately 140.0° C

If the specified value was obtained:

- End diagnosis and switch the ignition off.

- Replace the Engine Coolant Temperature (ECT) Sensor (G62). Refer to appropriate service manual.

- Go to Final procedures

If the specified value was not obtained:

Checking wiring

- Remove the Motronic Engine Control Module (ECM) (J623). Refer to appropriate service manual.

- Using a Multimeter, check the Engine Coolant Temperature (ECT) Sensor (G62) electrical harness connector terminals to the Motronic Engine Control Module (ECM) (J623) electrical harness connector T60 terminals for an open circuit according to the wiring diagram.

Specified value: scan tool display approximately -40.0° C

If the specified value was obtained:

- End diagnosis and switch ignition off.

- Replace the Engine Coolant Temperature (ECT) Sensor (G62). Refer to appropriate service manual.

- Go to Final procedures

If the specified value was not obtained:

Checking wiring

- Remove the Motronic Engine Control Module (ECM) (J623). Refer to appropriate service manual.

- Using a Multimeter, check the Engine Coolant Temperature (ECT) Sensor (G62) electrical harness connector terminals to the Motronic Engine Control Module (ECM) (J623) electrical harness connector T60 terminals for an open circuit according to the wiring diagram.

Specified value: 1.5 ohms Max.

If the specified value was not obtained:

- Check the wiring for a short circuit to Battery voltage, or an open circuit.

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

- If necessary, repair the faulty wiring connection.

- Go to Final procedures

If the specified value was obtained:

- Replace the Motronic Engine Control Module (ECM) (J623). Refer to appropriate service manual.

Final procedures

- Reinstall the engine cover with air filter, if necessary. Refer to the appropriate service manual.

- 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 ] Programming and Relearning.