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

PROCEDURE
- Disconnect ECT sensor harness connector.



- Check resistance between terminals 1 and 3 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 between ECT sensor and ECM as follows:
- Connect VAG 1598/19 test box to ECM wiring harness.
- Check Ground (GND) wire for continuity between ECT sensor connector terminal 3 and GND.

Specified Value: maximum 1.0 ohm

- Check signal wire for continuity between ECT sensor connector terminal 1 and test box socket 16A.

Specified Value: maximum 1.0 ohm

- Check both wires for short to each other.

If specified values are not obtained:



- Eliminate short or open circuit in wiring between ECT sensor and ECM connector -A- or engine Ground (GND).

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

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