Air Temperature Sensor ( Ambient / Intake ): Testing and Inspection

Intake Air Temperature (IAT) Sensor -G42, Checking

- Connect vehicle diagnostic, testing and information system VAS 5051 or VAG1551 scan tool and select engine electronics control module by entering address word "01 ". When doing this the ignition must be switched on. Refer to "Scan Tool Testing/Scan Tool Connecting and Initial Checks", Testing and Inspection

Indicated on display


Rapid data transfer HELP
Select Function XX


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

Indicated on display


Read Measuring Value Block HELP
Input Display Group Number XXX


- Press buttons -0-, -0- and -4- to select Display Group 4 and confirm entry with -Q- button.

Indicated on display: (1 ...4 = display fields)


Read Measuring Value Block 4 ->
1 2 3 4


- Check display value for intake air temperature sensor (display field 4):

Display Group 004:

Checking wiring:
- Switch ignition off.
- Connect test box VAG1598/31 to wiring harness for engine control module. Do not connect to the engine control module itself. Refer to "Scan Tool Testing/Wiring And Component Check With VAG1598/31 Test Box", Testing and Inspection







- Check for open circuit in wiring between test box and 2 pin harness connector using wiring diagram.

Specified value: max. 1.5 Ohms

Terminal on 2-pin Contact on control
harness connector module connector
or test box
1 85
2 108

- Check wiring for short circuits to each other between contacts 1 and 2 on 2-pin connector. Also test for short circuits to B+ or Ground (GND).

If no malfunction in wire is detected:

Checking sender







- Measure resistance between contacts 1 (signal) and 2 (Ground GND)) on connector for Intake Air Temperature (IAT) sensor -G42.

Temperature °C Resistance kOhms
-20 approx. 13.8
0 approx. 55
20 approx. 2.4
40 approx. 1.1
60 approx. 0.6

- If value does not match the specification, replace intake air temperature sensor.
- In order to install a new sensor, the intake manifold must first be removed.