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

Checking Engine Coolant Temperature Sensor

NOTE:
^ For functional testing of the ECT sensor, Also Refer to On Board Diagnotic, "Read Measuring Value Block" function 08, display group 001, display field 1. Testing and Inspection

- Disconnect ECT sensor harness connector.

Engine Coolant Temperature Sensor:

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

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 test box with VAG 1598/11 adapter harness to ECM wiring harness. Connecting VAG 1598/31 Test Box
^ Adapter harness is not connected to ECM.
- Check Ground (GND) wire for continuity between ECT sensor connector terminal 2 and GND.
^ Specified value: maximum 1 (ohm)
- Check signal wire for continuity between ECT sensor connector terminal 1 and test box socket 15.
^ Specified value: maximum 1 (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 -C- and/or GND.

ECT sensor ECM connector C
connector terminal terminal
1 15
2 Ground(GND)

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