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4-Pin Engine Coolant Temperature Sensor, Checking






4-Pin Engine Coolant Temperature Sensor, Checking

• This procedure is used to diagnose the 4 pin Engine Coolant Temperature (ECT) Sensor (G62) Phased in modification. Refer to => [ 2-Pin Engine Coolant Temperature Sensor, Checking ] 2-Pin Engine Coolant Temperature Sensor, CheckingEngine Coolant Temperature (ECT) Sensor (G62) for 2 pin from June 2005 diagnosis.

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 Motronic Engine Control Module (ECM) ( J623 ) Fuse (S243) 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 the ignition on.

- Using the scan tool, check the coolant temperature:





If the specified value is not obtained:

- 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.

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

- Replace the the Engine Coolant Temperature (ECT) Sensor ( G62) Refer to Fuel Injection and Ignition Repair Information.

Checking internal resistance

- Disconnect the Engine Coolant Temperature (ECT) Sensor (G62) electrical harness connector - 2 -.





- Using a multimeter, check the Engine Coolant Temperature (ECT) Sensor (G62) terminals 3 to 4 for resistance.





Use the chart below for the specified values:

• Area A: Resistance values 0 to 50° C.

• Area B: Resistance values 50 to 100° C.

Specified values:





• Range A, 30° C equals a resistance of 1.5 to 2.0 kohms

• Range B, 80° C equals a resistance of 275 to 375ohms

If any of the specified values was not obtained:

- Replace the Engine Coolant Temperature (ECT) Sensor ( G62) Refer to Fuel Injection and Ignition Repair Information.

°Testing if display is approx. - 40.0 C:

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





- Using a jumper wire, connect the Engine Coolant Temperature (ECT) Sensor (G62) electrical harness connector terminals 3 to 4.

- Check the value indicated on the scan tool display.

If the value jumps to approx. 140.0° C

- End diagnosis and switch the ignition off.

- Replace the Engine Coolant Temperature (ECT) Sensor ( G622) Refer to Fuel Injection and Ignition Repair Information.

If indication remains at approx. -40.0° C:

°Testing if display approx. 140.0 C:

- Disconnect the Engine Coolant Temperature (ECT) Sensor (G62) electrical harness connector - 2 -.





If indication jumps to approx. -40.0° C:

- End diagnosis and switch ignition off.

- Replace the Engine Coolant Temperature (ECT) Sensor ( G62) Refer to Fuel Injection and Ignition Repair Information.

If indication remains at approx. 140.0° C:

Checking wiring

If the manufacturers test box is being used. Perform the following step.

- Install the test box. Refer to Fuel Injection and Ignition Repair Information.

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

- Remove the Motronic Engine Control Module (ECM) ( J623). Refer to => [ Engine Control Module, Replacing ] Service and Repair.

- 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 T121 terminals for an open circuit according to the wiring diagram.









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, lose or broken terminals.

- If necessary, repair the faulty wiring connection.

If no malfunction is detected in the wiring:

- Replace the Motronic Engine Control Module (ECM) (J623). Refer to => [ Engine Control Module, Replacing ] Service and Repair.

Final procedures

After 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 ] Monitors, Trips, Drive Cycles and Readiness Codes.

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