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

Engine Coolant Temperature (ECT) Sensor -G62-, Checking

Requirement
- Engine cold

Work sequence
- Connect vehicle diagnostic, testing and information system VAS 5051 and select vehicle system "01 - Engine electronics" from list. Engine must be idling. Connecting VAS 5051 Scan Tool







Indicated on VAS 5051:
- From list -1- select diagnostic function "08 - Reading measured value block".







Indicated on VAS 5051:
1 - Enter display group
- Use keypad -2- to enter "004" for "Display group number 004" and confirm by touching Q key.







Indicated on VAS 5051:
- Check display in zone -3-.

Display Group 004:

NOTE: With engine cooled down, displays in zones 3 (coolant temperature) and 4 (intake air temperature) must be roughly equal.

If display in zone 3 is not realistic:
- Disconnect connector at Engine Coolant Temperature (ECT) sensor -G62-.
- Connect test box V.A.G 1598/31 at wiring harness to engine control module. Actual engine control module is not to be connected. Wiring And Component Check Using Test Box V.A.G 1598/31
- Check wiring from 4-pin connector ...
- ... to engine control module for open circuit and short to positive/Ground.

4-pin connector at Test box V.A.G
wiring harness, socket 1598/31, socket
3 108
4 93

Resistance: max. 1.5 Ohm

- Eliminate open circuit in wiring/short circuit if necessary.

If no fault is found in wiring:
- Replace Engine Coolant Temperature (ECT) sensor -G62-.

NOTE: For ECT sensor -G62-, ranges A and B indicate resistance values for temperature ranges 0...50 degree C and 50...100 degree C respectively.







Readings:
- 30 degree C corresponds to a resistance of 1500...2000 Ohm
- 80 degree C corresponds to a resistance of 275...375 Ohm