Intake Air Temperature (IAT) Sensor, Checking
Intake Air Temperature (IAT) Sensor, Checking
NOTE: When servicing terminals in the harness connector for the Mass Air Flow (MAF) sensor or Intake Air Temperature (IAT) sensor, use only gold-plated terminals.
Recommended special tools and equipment
- V.A.G 1526 multimeter or V.A.G 1715 multimeter
- V.A.G 1594 connector test kit
- Wiring diagram
- Chilling spray (commercially available)
Test requirements
- Corresponding fuses on fuse holder in instrument panel, left side, for Intake Air Temperature (IAT) Sensor -G42- 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.
- All electrical consumers such as, for example, lights and rear window defroster must be switched off.
- Ground (GND) connections between engine and chassis must be OK.
- For vehicles with automatic transmission, selector lever must be in -P-.
- Ignition switched off.
Function test
Observe safety precautions.
Observe rules for cleanliness.
- Remove intake air hose between Throttle Valve Control Module -J338- and Mass Air Flow (MAF) Sensor -G70-.
- Connect diagnostic tester.
- Start engine and let run at idle.
- Under address word 33, select "Diagnostic mode 1: Check measured values."
- Select the measuring value "PID 15 ($F): Intake air temperature".
- Check specified value of intake air temperature:
- Remember the intake air temperature value.
- Spray the sensor -arrow- with commercially available chilling spray and watch the intake air temperature value while doing this.
The temperature value must decrease.
- End diagnosis and switch ignition off.
If specified value is not obtained:
- Disconnect 5-pin connector from Mass Air Flow (MAF) Sensor -G70- with Intake Air Temperature (IAT) Sensor -G42-.
Checking resistance
- Check resistance of Intake Air Temperature (IAT) Sensor -G42- between terminals 3 and 4 using adapter cables.
Range A displays resistance values for the temperature range of 0 to 50 degrees C, range B displays resistance values for the temperature range of 50 to 100 degrees C.
Read-out examples:
- 30 degrees C is in range A and corresponds to a resistance of 1.5 to 2.0 kohms
- 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 Mass Air Flow (MAF) Sensor -G70- with Intake Air Temperature (IAT) Sensor - G42-.
NOTE: The Intake Air Temperature (IAT) sensor is a component of the Mass Air Flow (MAF) sensor and cannot be replaced individually.
- Erase DTC memory of Engine Control Module (ECM), Diagnostic mode 4: Reset/erase diagnostic data. 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 94-pin connector of wiring harness, connecting test box for wiring test.
Engine Control Module (ECM) is not connected.
- Check wires between test box and 5-pin connector to Engine Control Module (ECM) for open circuit according to wiring diagram.
Terminal 3 + socket 13
Terminal 4 + socket 64
Wire resistance: max. 3.0 ohms
- Also check wires for short circuit to each other.
Specified value: infinity ohms
- Erase DTC memory of Engine Control Module (ECM), Diagnostic mode 4: Reset/erase diagnostic data. 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-.