Intake Air Temperature (IAT) Sensor, Checking

Intake Air Temperature Sensor, Checking

Special tools and equipment
- VAG 1551/1552 Scan Tool using VAG 1551/3 adapter cable
- VAG 1598/18 Test Box
- Fluke 83 multimeter (or equivalent)
- VW 1594 Adapter kit
- Wiring diagram
- Freeze-spray (commercially available)

Test sequence
- Connect VAG 1551 (VAG 1552) Scan Tool. Selectable Functions When Using VAG1551/1552 or VAS5051
- With ignition switched on but engine not running, press buttons -0- and -1- to select "Engine electronics" address word 01.

Display will appear as shown


Rapid data transfer HELP
Select function XX


- Press buttons -0- and -8- to select "Read measuring value block".
- Press -Q- button to enter selection.

Display will appear as shown


Read measuring value block HELP
Input display group number XXX


- Press buttons -0-, -0- and -3- to select "Display group number 3".
- Press -Q- button to enter selection.

Display will appear as shown (1 to 4 = Display fields)


Read measuring value block 3 ->
1 2 3 4

- Check specification for Intake Air Temperature sensor (Display field 4).

Display Group 3:

Evaluating display group 3






Wiring, checking
- Switch ignition off.







- Connect VAG 1598/18 Test Box to ECM wiring harness.







- Disconnect 2-pin connector for Intake Air Temperature sensor -G72- (arrow).







- Check wiring for open circuit between Test Box and 2-pin connector using wiring diagram.
terminal 1 + socket 36
terminal 2 + socket 33
- wire resistance: Max. 1.5 Ohms
- Check wiring between ECM connector and 2-pin connector terminal 2 for short to wire terminal 1 and to vehicle Ground using wiring diagram.
terminal 2 + socket 36
- specification: infinity Ohms
- Check both wires for possible shorting to Battery positive.
- specification: infinity Ohms

If wiring OK:
- Measure resistance between terminals 1+2 of Intake Air Temperature sensor -G72-.

If specification not obtained:
- Replace Intake Air Temperature sensor -G72-

Continuation of check when display = ambient temperature







- Remove Intake Air Temperature sensor -G72- (leave connected).
- Read Intake Air Temperature value in Display field 4
- Spray sensor with (commercially available) freeze-spray while observing temperature value
- temperature value must decrease

If value does not decrease:
- Replace Intake Air Temperature sensor - G72-.
- Read-out Readiness code. Monitors, Trips, Drive Cycles and Readiness Codes

If DTC memory has been erased:
- Create Readiness code. Monitors, Trips, Drive Cycles and Readiness Codes