The Motronic ECU in our UrS4 and S6 cars uses a number of inputs including the intake air temperature to decide things about boost, timing and fuel. The G42 intake air sensor is located on the throttle body, as shown here:



The ECU uses the G52 signal to dial back timing (and power) to prevent pinging if the intake air temp is too high.

The function of the G42 is described in VAG self study guide as:


Part number is 034905379B which is very common across the Audi I5 from 1985 to 1997, as shown here:


If there are issues, you might get a Check Engine Light (CEL). Blinking out the fault code (or checking with a VAG tool) would reveal:

2322 (Blink Fault Code), 00523 VAG1551/2 Fault Code Number
Inlet air temp sensor (G42)
Open or short circuit, Defective sensor or wiring
Symptom: Slight power loss, Increase in fuel consumption
(Reference SJM Autotechnik)

The G42 IAT is connected to the ECU via pin T44/55 with a brown striped blue wire (BR/BL). A digital multimeter can be used to measure the resistance of the two-pin device G42 intake air sensor with the connector harness removed. With the engine OFF long enough to cool sufficiently, at an ambient air temperature of 20 degrees, a value of 450-650 ohms should be measured across G42.

From SJM Autotechnik, via S2central.net:



This will be on the exam.