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

NOTE:
^ For functional testing of the Engine Coolant Temperature (ECT) sensor, Also Refer to On Board Diagnostic, "Read Measuring Value Block" function 08, display group 001, display field 1.

PROCEDURE
- Disconnect ECT sensor harness connector.

Engine Coolant Temperature Sensor:

- Check resistance between terminals 1 and 2 of sensor. Specified values:
^ At approx. 20°C (68°F) coolant temperature, approx. 2.5K ohms
^ At approx. 80°C (176°F) coolant temperature, approx. 330 ohms

If specified values are not obtained:
- Replace ECT sensor.

If specified value is obtained, check wiring from sensor to ECM as follows:
- Connect VAG 1598/19 test box to ECM wiring harness. Refer to Computer and Control Systems, System Diagnosis, VAG 1598 Pin Out Box Connecting. Connecting VAG 1598/31 Test Box
- Check Ground (GND) wire for continuity between ECT sensor connector terminal 2 and GND.
^ Specified value: maximum 1.0 ohm
- Check signal wire for continuity between ECT sensor connector terminal 1 and test box socket A 16.
^ Specified value: maximum 1.0 ohm
- Check both wires for short to each other.

If specified values are not obtained:
- Repair short and/or break in wiring between ECT sensor and ECM connector and/or GND.

ECT sensor ECM connector
connector terminal terminal
1 A 16
2 Ground(GND)

If there is no short or break in wiring, and ECT sensor is OK:
- Replace ECM.