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Engine Coolant Temperature Sensor G62, Checking






Engine Coolant Temperature Sensor G62, Checking

CAUTION!
Cooling system is under pressure.

Danger of scalding when opening!

Special tools, testers and auxiliary items required

Multimeter

jumper wire

wiring diagrams

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

Test requirements

Fuses for Engine Control Module (ECM) (J623) 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.

Function test

- Connect the scan tool.

- Switch ignition on.

- Select "Diagnostic mode 1: Check measured values".

- Select measured value "PID 05: Coolant temperature".

- Check specified value of coolant temperature:





If specified value is not obtained:

- Continue test according to the following table:





If specified value is obtained:

- Start engine and let it run at idle.

Temperature value must increase uniformly in increments of 1.0° C.

If the engine shows problems in certain temperature ranges and if the temperature does not climb uniformly, the temperature signal is intermittent.

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

°Testing if display approx. -40.0 C:

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

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





- Using jumper wire , bridge electrical connector terminals 1 + 2 together and observe indication on display.

If indication jumps to approx. 140.0° C:

- End diagnosis and switch ignition off.

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

If indication remains at approx. -40.0° C:

- Check the wiring for a short circuit to Battery positive (+) or an open circuit.

- If necessary, repair the wiring connection.

- End diagnosis and switch ignition off.

°Testing if display approx. 140.0 C:

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





If indication jumps to approx. -40.0° C:

- End diagnosis and switch ignition off.

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

- End diagnosis and switch ignition off.

If indication remains at approx. 140.0° C:

Checking wiring

- Using a Multimeter , check the following wiring connection for an open circuit.









Specified resistance 1.5 ohms max.

If the specification is not obtained:

- Check the wiring for a short circuit to Battery positive (+) or an open circuit.

- If necessary, repair the wiring connection.

If no malfunctions are found in the wiring:

- Using a multimeter , check Engine Coolant Temperature (ECT) Sensor (G62) electrical connector terminals 1+2 for resistance.





Area A: Resistance values for temperature range 0 to 50°C.

Area B: Resistance values for temperature range 50 to 100°C.

Read-out examples:





30° C is in range A and corresponds to a resistance of 1.5 to 2.0 kohms

80° C is in range B and corresponds to a resistance of 275 to 375ohms

If the specification is not obtained:

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

If the specification is obtained:

- 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 OK:

- Replace the Engine Control Module (ECM) (J623 ) => [ Motronic Engine Control Module, Replacing ] Motronic Engine Control Module, Replacing.

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, Setting ] Readiness Code, Setting.

End of Diagnosis.