Engine Coolant Temperature Sensor, Checking

INTAKE AIR TEMPERATURE SENSOR, CHECKING

Special Tools, Testers And Auxiliary Items
- VAG 1551 Scan Tool (ST) or vehicle system tester VAG 1552 with VAG 1551/3 adapter cable
- VAG 1598/18 test box
- Multimeter (Fluke 83 or equivalent)
- VW 1594 connector test kit
- Wiring diagram

Test Conditions
- Engine cold

Test sequence
- Start engine and run at idle speed.
- Connect VAG 1551 scan tool (VAG 1552) and insert "Engine Electronics" address word 01. Carry out selection at idle. Refer to "On-Board Diagnostic". Testing and Inspection

Indicated on display

Rapid data transfer HELP
Select function XX

- Press buttons -0- and -8- to select "Read Measuring Value Block" function 08.
- Press -Q- button to confirm input.

Indicated on display

Read measuring value block HELP
Input display group number XXX

- Press -0-, -0- and -1- to input display group number 001.
- Press -Q- button to confirm input.

Indicated on display (1, 2, 3 and 4 = Display fields)

Read measuring value block 1 ->
1 2 3 4

NOTE: If something different is indicated on the display:
See Scan tool operating instructions.

Functional Check Of Sensor





NOTE:
- Depending upon the temperature level, the display on VAG 1551 scan tool will jump by 2-5 °C.
- If irregular engine running occurs in certain temperature ranges and the temperature value does not increase without interruption, the temperature signal is temporarily interrupted and the sensor must be replaced.

- Press -> button.
- Press buttons -0- and -6- to select "End Output" function 06.
- Press -Q- button to confirm input.
- Switch ignition off

Continuation Of Check When Display = 77.7 °C





- Connect VAG 1598/18 test box to ECM wiring harness.





- Disconnect 4-pin harness connector -1- from engine coolant temperature sensor G62 -2-.





- Check wiring for open circuits between test box and 4-pin connector, according to wiring diagram.
- Terminal 1 and test box socket 14
- Terminal 3 and test box socket 33
- Wire resistance: Max. 1.5 Ohms
- Check wiring between ECM connector and 4-pin connector terminal 3 for short circuit to terminal 1 and/or chassis ground, according to wiring diagram.

Specification: Infinity Ohms (no continuity)

- Additionally check wires for short to battery positive (B+).

Specification: Infinity Ohms (no continuity)

If no wiring malfunction is detected:
- Measure resistance at engine coolant temperature sensor G62 terminals 1 and 3.

Resistance Specifications





The diagram is valid for engine coolant temperature sensor G62 and intake
air temperature sensor G72.

A - resistance values for the temperature range 0 ° - 50 °C (32 ° - 122 °F)
B - resistance values for the temperature range 50 ° - 100 °C (122 ° - 212 °F)

Examples:

- 30 °C corresponds to a resistance value of 1500 - 2000 Ohms
- 80 °C corresponds to a resistance value of 275 - 375 Ohms

If the specification is not attained:
- Replace engine coolant temperature sensor G62.