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

REQUIREMENT
^ Engine cold

CHECKING ENGINE COOLANT TEMPERATURE SENSOR
- Connect VAG 1551 Scan Tool (ST) and enter address word 01 for "Engine Electronics" (select functions with engine idling).

^ Indicated on display:

Rapid data transfer HELP
Select function XX

- Press buttons -0- and -8- to select the "Read Measuring Value Block" function.
- Press -Q- button to confirm input.

^ Indicated on display:

Read measuring value block HELP
Input display group number XX

- Press buttons -0- and -1- to enter display group 01.
- Press -Q- button to confirm input.

^ Indicated on display (1 - 4 = display fields)

Read measuring value block 1 HELP
1 2 3 4

NOTE: If something different is indicated on the display, check the VAG 1551 Scan Tool operating instructions.

- Read Engine Coolant Temperature (ECT) (G62) value in display field 2.

NOTE:
- Temperature must increase uniformly and without interruption.

- If the VAG 1551 Scan Tool display jumps by 2 - 5°C, this is caused by the Motronic Engine Control Module (ECM) (J220), and not by a malfunctioning Engine Coolant Temperature Sensor.

- Display of 78.4°C indicates an open circuit.

- If irregular engine running occurs in certain temperature ranges and the temperature figure does not increase without interruption, the temperature signal is temporarily interrupted and the Engine Coolant Temperature Sensor must be replaced.

- Press --> button.
- Press buttons -0- and -6- to select the "End Output" function.
- Press -Q- button to confirm input.
- If the temperature value does not change:

- Carry out electrical testing, test step 19
- If necessary, replace Engine Coolant Temperature Sensor.

CAUTION: Release pressure from cooling system before replacing Engine Coolant Temperature Sensor.