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

CHECKING ENGINE COOLANT TEMPERATURE SENSOR

Functional Check
- Check using VAG 1551 Scan Tool (ST) in Function 08, "Read measuring value block", with engine at idle.

Special Tools
- Scan Tool VAG 1551 using adaptor cable VAG 1551/1.

Test Conditions
- Engine cold.
- Scan Tool VAG 1551 connected and Function 08: "Read measuring value block" selected (Display group number 01).

^ Display will appear as shown: (1 to 4 = Display channels)

Read measuring value block 1 -->
1 2 3 4

NOTE: If something different is displayed, refer to Scan Tool operating instructions.

Test Sequence
- Observe Engine Coolant Temperature value in display channel 2.
- Value must increase uniformly without interruption.

NOTE:
- If engine runs irregularly in certain temperature ranges and the displayed temperature does not increase uniformly, temperature signal is intermittent requiring sensor replacement.

- If the Scan Tool display jumps by 2 to 5°C, this is caused by the Engine Control Module (ECM) and not a malfunctioning sensor.

- Interruption will be displayed as - 40°C.

- Press --> button.
- Input 06 to select Function "End output" and confirm with Q button.
- If Engine Coolant Temperature value does not change:

- Perform electrical check. Refer to Diagnostic Charts / VAG 1598 Pin Out Box / Electrical Checks / Test Step 13. Testing and Inspection
- Replace Engine Coolant Temperature (ECT) sensor G62, after first releasing cooling system pressure.