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

Intake Air Temperature (IAT) sensor - G42-, checking

Installation location of sensor (common component: MAF sensor and intake air temperature sensor in air filter element).

- Connect Vehicle Diagnostic, Testing and Information System VAS 5051 or V.A.G 1551 Scan Tool and select engine electronics control module with "Address word" 01. For this purpose, ignition must be switched on.

Indicated on display
Rapid data transfer HELP
Select function XX


- Press keys 0 and 8 for function "Read measured value block" and confirm entry with Q key.

Indicated on display

Read measured value block HELP
Enter display group number XXX

- Press keys 0, 0 and 4 for "display group number 4" and confirm entry with Q key.

Indicated on display: (1...4 display zones)


Read measured value block 4 ->
1 2 3 4


- Check specified result for intake air temperature sensor (display zone 4):

Display Group 4:

Checking wiring
- Switch ignition off.
- Connect test box VAG 1598/31 to wiring harness for engine control module; do not connect engine control module. Connecting VAG 1598/31 Test Box
- Disconnect connector to MAF sensor.







- Check for shorts between two lines.

5-pin connector on
wiring harness, socket Test box V.A.G 1598/31, socket

1 27

Specified value: infinity Ohm (no connection)







- Check for open circuit and short to positive or Ground in following wiring connections:

5-pin connector on
wiring harness, socket Test box V.A.G 1598/31, socket
1 85 or 26 (according to model year)
3 27

Wire resistance: max. 1.5 Ohm
- Correct any open/short circuit as necessary.

If no wiring malfunction is detected:
- Replace intake air temperature (IAT) sensor -G42- (common component: Mass Air Flow (MAF) sensor -G70- and intake air temperature (IAT) sensor -G42-).