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

WARNING: This page is about a different car, the 2006 Audi A4, 2005 Audi A4, 2004 Audi A4, 2003 Audi A4, and 2002 Audi A4. However, it is still accessible from the selected car via links, so may be relevant.

Fig 1: Identifying Special Tools - Intake Air Temperature (IAT) Sensor -G42-, Checking

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Special tools and workshop equipment required

V.A.G 1526 A Multimeter
V.A.G 1594 A Connector test kit
V.A.G 1598/31 Test box
VAS 5051 Vehicle diagnostic, testing and information system with VAS 5051/1 B Adapter

Component location → Component locations, overview

Work sequence

Connect vehicle diagnostic, testing and information system VAS 5051. Refer to VAS 5051 vehicle diagnostic, testing and information system, connecting and selecting functions and select vehicle system "01 -Engine electronics" in selection. Engine must be running at idle.

Fig 2: Diagnostic System VAS 5051: Display

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Display on VAS 5051:

Under -1- select diagnostic function "08 - Read measured value block".

Fig 3: Diagnostic System VAS 5051: Display

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Display on VAS 5051:

1 - Display group input

Enter "004" for "display group number 004" in zone -2- and confirm entry by pressing -Q- button.

Fig 4: Diagnostic System VAS 5051: Display

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Display on VAS 5051:

Check Intake Air Temperature (IAT) sensor in display zone -4-.

	Display zones
	1	2	3	4
Display group 004: Intake air temperature with engine at idle
Display	xxxx rpm	xx.x V	xxx.x ° C	xxx.x ° C
Display	Engine speed	Battery voltage (B+)	Coolant temperature	Intake air temperature
Range				-48.0...143.0 ° C
Specified value	xxxx rpm	12.0...15.0 volts	80.0...110.0 ° C	Between ambient temperature and up to 110 ° C 1)

1) If a temperature is displayed which deviates greatly from the ambient temperature of the sensor, check sensor and sensor wiring for terminal resistances and open circuit.

Exit function "08 - Read measured value block" by pressing ← button.

Checking wiring

Disconnect connector to Intake Air Temperature (IAT) sensor -G42-.
Connect test box V.A.G 1598/31 to wiring harness for ECM; do not connect ECM. Refer to Electrical testing using VAG1598/31 test box .

Fig 5: Identifying 2-Pin Electrical Harness Connector & Terminals

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Check for open circuit, short to positive, or short to ground in following wiring connections:

Connector Terminal	Test box V.A.G 1598/31 Socket
1	85
2	108

Test for short circuits between two wires.
Repair any open/short circuit as necessary.

If no wiring problems are found:

Checking sensor

Fig 6: Identifying Intake Air Temperature (IAT) Sensor -G42- Resistance

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Connect multimeter to sensor to measure resistance.

Specifications

Temperature ° C	Resistance k Ω
-20	approx. 13.8
0	approx. 5.5
20	approx. 2.4
40	approx. 1.1
60	approx. 0.6

If the specified values are not obtained:

Replace Intake Air Temperature (IAT) sensor -G42-.