Intake Air Temperature (IAT) Sensor, Checking

Intake Air Temperature (IAT) Sensor, Checking

NOTE: Use only gold-plated terminals when servicing terminals in the harness connector.

Recommended special tools and equipment
- V.A.G1526 multimeter or V.A.G1715 multimeter
- V.A.G1594 connector test kit
- Wiring diagram
- Chilling spray (commercially available)

Test requirements







- Fuses on E-box in engine compartment, left side, must be OK.

NOTE: Fuses on this fuse holder are labelled "SB" in the wiring diagram.







- Fuses on fuse holder in instrument panel, left side, must be OK.

NOTE: Fuses on this fuse holder are labelled "SC" in the wiring diagram.

- Battery voltage must be at least 11.5 Volts.
- Ground (GND) connections between engine and chassis must be OK.
- All electrical consumers such as, lights and rear window defroster must be switched off.
- Ignition switched off.

Function test
Observe safety precautions.
Observe rules for cleanliness.

- Connect diagnostic tester.
- Switch ignition on.
- Under address word 33, select "Diagnostic mode 1: Checking measured values."
- Select measuring value "PID 15 ($F): Intake air temperature".
- Check specified value of intake air temperature:







- Remember intake air temperature value.
- Remove engine cover, removing and disassembling air filter/engine cover.
- Disconnect 2-pin connector from Intake Air Temperature (IAT) Sensor -G42-.
- Remove Intake Air Temperature (IAT) Sensor -G42-. Re-connect connector.







- Spray sensor with commercially available chilling spray -arrow- and observe temperature value while doing this.

The temperature must decrease.
- End diagnosis and switch ignition off.

If specified values are not obtained:

Checking resistance







- Check resistance of Intake Air Temperature (IAT) Sensor -G42- between terminals using adapter cables.







- Range A displays resistance values for temperature range of 0 to 50 degrees C, range B displays resistance values for temperature range of 50 to 100 degrees C.

Read-out examples:
- 30 degrees C is in range A and corresponds to a resistance of 1500 to 2000 Ohms
- 80 degrees C is in range B and corresponds to a resistance of 275 to 375 Ohms

NOTE: Intake Air Temperature (IAT) Sensor -G42- has a negative temperature coefficient (NTC). This means: the higher the temperature the lower the resistance value.

If specified value is not obtained:
- Replace Intake Air Temperature (IAT) Sensor -G42-.
- Erase DTC memory of Engine Control Module (ECM). Diagnostic Mode 04 - Erase DTC Memory
- Generate readiness code. Monitors, Trips, Drive Cycles and Readiness Codes

If specified value is obtained:
- Check wires to Engine Control Module (ECM) according to wiring diagram.

Checking wires to Engine Control Module (ECM)
- Connect test box to 60-pin connector of wiring harness. Test Box, Connecting For Wiring Test

Engine Control Module (ECM) is not connected.







- Check wires between test box and 2-pin connector to Engine Control Module (ECM) for open circuit according to wiring diagram.

Terminal 1 + socket 13
Terminal 2 + socket 14

Wire resistance: max. 3.0 Ohms

- Check wires for short circuit to each other.

Specified value: Infinity Ohms

- Erase DTC memory of Engine Control Module (ECM). Diagnostic Mode 04 - Erase DTC Memory
- Generate readiness code. Monitors, Trips, Drive Cycles and Readiness Codes

If no malfunctions are detected in the wires and the resistance value is OK:
- Replace Engine Control Module (ECM) -J623-