With Generic Scan Tool

Intake Air Temperature (IAT) Sensor, Checking

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






- The respective fuses of Motronic Engine Control Module (ECM) -J220- must be OK.
- Parking brake must be engaged or else daylight driving lights will be switched on.
- For vehicles with automatic transmission, selector lever must be in -P-.

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






If specified value is not obtained:
- Continue test according to the following table:






1) If a temperature is indicated which is below the ambient temperature of sensor, first check sensor wires for contact resistance. Note that while the vehicle is standing still the sensor might warm up due to radiant heat.

If specified value is obtained:






- Disconnect 2-pin connector -1- from Intake Air Temperature (IAT) Sensor -G42- (-2-).
- Remove Intake Air Temperature (IAT) Sensor -G42- and reconnect to connector.
- Seal threaded bore for sensor.
- Remember intake air temperature value.





- Spray sensor with commercially available chilling spray while observing temperature value. The temperature must decrease.
- End diagnosis and switch ignition off.

If intake air temperature does not drop:
- Replace Intake Air Temperature (IAT) Sensor -G42-.

- Erase DTC memory of Engine Control Module (ECM), Diagnostic mode 4: Reset/erase diagnostic data.
- Generate readiness code

Continuation of test if indication is approx. -46.5°C:






- Disconnect 2-pin connector -1- from Intake Air Temperature (IAT) Sensor -G42- (-2-).






- Bridge terminals 1 + 2 of connector using the respective adapter cables while observing the indication on display.

If indication jumps to approx 141.0°C:
- End diagnosis and switch ignition off.
- Replace Intake Air Temperature (IAT) Sensor -G42.
- Erase DTC memory of Engine Control Module (ECM), Diagnostic mode 4: Reset/erase diagnostic data.
- Generate readiness code.

If indication remains at approx 46.5°C:
- End diagnosis and switch ignition off.
- Check wires according to wiring diagram.

Continuation of test if indication is approx. 141.0°C:






- Disconnect 2-pin connector -1- from Intake Air Temperature (IAT) Sensor -G42- (-2-).

If indication jumps to approx -46.5°C:
- End diagnosis and switch ignition off.
- Replace Intake Air Temperature (IAT) Sensor -G42-.
- Erase DTC memory of Engine Control Module (ECM), Diagnostic mode 4: Reset/erase diagnostic data.
- Generate readiness code.

If indication remains at approx 141.0°C:
- End diagnosis and switch ignition off.
- Check wires according to wiring diagram.

Checking wiring

- Connect test box to control module wiring harness.

Vehicles > 08.99






- Check wires between test box and 2-pin connector to Engine Control Module (ECM) for open circuit according to wiring diagram.
Terminal 1+socket 36
Terminal 2 + socket 33
Wire resistance: max. 1.5 ohms

Vehicles 09.99 >






- Check wires between test box and 2-pin connector to Engine Control Module (ECM) for open circuit according to wiring diagram.
Terminal 1 + socket 54
Terminal 2 + socket 67
Wire resistance: max. 1.5 ohms

Continue for all vehicles

- Check wires for short circuits among one another.
Specified value: infinite ohms

If no malfunctions are found in wire:






- Measure resistance at Intake Air Temperature (IAT) Sensor -G42- (-2-), terminals 1 (signal) and 2 (Ground GND).






Range A displays resistance values for the temperature range of 0 to 0.50°C, range B displays resistance values for the temperature range of 50 to 0.100°C.

Read-out examples:
30°C is in range A and corresponds to a resistance of 1.5 to 2.0 k ohms
80°C is in range B and corresponds to a resistance of 275 to 375 ohms

If specified value is not obtained:
- Replace Intake Air Temperature (IAT) Sensor -G42-.
- Erase DTC memory of Engine Control Module (ECM), Diagnostic mode 4: Reset/erase diagnostic data.
- Generate readiness code.

If no malfunctions are detected in the wires and the resistance values are OK:
- Replace Motronic Engine Control Module (ECM) -J220-.