Intake Air Temperature (IAT) Sensor G42 , Checking

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







Recommended special tools and equipment
- VAG1526A multimeter
- VAG1594A connector test kit
- VAG1598/31 test box

NOTE: Intake Air Temperature (IAT) Sensor -G42- is integrated in Mass Air Flow (MAF) Sensor - G70-.

Test requirements:
- Fuses for engine electronics OK
- Ignition switched off.

Checking function
- Connect diagnostic tester. VAS 5051, Connecting and Select Functions
- Start engine and let run at idle.
- In diagnostic function "33 - OBD", select "Mode 1: Checking measured values."
- Select desired measuring value "PID 15: Intake air temperature".
- Specified value: approx. ambient temperature

NOTE: If a temperature is indicated which differs greatly from ambient temperature of sensor, check sensor and sensor wires for contact resistances and open circuit.

- End diagnosis and switch ignition off.

If indications do not resemble description:

Checking wire connections







- Disconnect harness connector (arrow) at Mass Air Flow (MAF) sensor -G70-.
- Connect test box to wiring harness of Engine Control Module (ECM); ECM is not connected.







- Check the following wire connection for open circuit according to wiring diagram:

Harness connector Terminal Test box Socket
5 26

- Specified value: Wire resistance max 1.5 Ohms

- Check wires for short circuit to each other as well as to B+ and Ground (GND).
- Specified value: infinity ohm (no continuity)
- If necessary, repair wire connection.

If no malfunctions are found in wires:
- Replace Mass Air Flow (MAF) Sensor -G70-.

Final procedures
After repair work, the following work steps must be performed in the mentioned sequence:
1. Check DTC memory. Diagnostic Mode 03 - Read DTC Memory
2. If necessary, erase DTC memory. Diagnostic Mode 04 - Erase DTC Memory
3. If DTC memory was erased, generate readiness code.

- End diagnosis and switch ignition off.