Intake Air Temperature (IAT) Sensor - G42-, Checking

Intake Air Temperature (IAT) sensor -G42, checking

Location of sensor (mass air flow sensor and intake air temperature sensor are combined as one component in air filter housing).

- Connect Vehicle Diagnostic, Testing and Information System VAS5051 or VAG 1551 Scan Tool and select engine electronics control module by entering address word "01", [1][2]Scan Tool Connecting and Initial Checks. When doing this the ignition must be switched on.

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 to 4 = display fields)


Read Measuring Value Block 4 ->
1 2 3 4


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







Checking wiring
- Switch ignition off.
- Connect VAG 1598/31 test box to wiring harness for engine control module. DO NOT connect to the engine control module itself, Connecting VAG 1598/31 Test Box
- Disconnect harness connector from mass air flow sensor See component locations overview.







- Check for short circuit between wires:

5-pin connector on VAG 1598/31 test
wiring harness, socket box socket
1 27

Specification: infinity ohms (no connection)







- Check for open circuit and short to B+ or Ground (GND) in the following wiring connections:

5-pin connector on VAG 1598/31
wiring harness, socket test box socket
1 85
3 27

Resistance in wiring: max. 1.5 ohms

- Correct any open/short circuit as necessary.

If no wiring malfunction is detected:
- Replace Intake Air Temperature (IAT) sensor -G42. (Mass Air Flow (MAF) sensor and Intake Air Temperature (IAT) sensor are combined as one component in air filter housing).
- Display readiness code, Readiness Code Reading. Readiness code must be generated if DTC memory was erased, Readiness Code, Generating