Intake Air Temperature Sensor, Checking

Intake Air Temperature Sensor, Checking

Recommended Special Tools, Workshop Equipment, Testers, Measuring Instruments and Auxiliary Items
- V.A.G 1526 portable multimeter or V.A.G 1715 multimeter
- Adapter set V. A. G 1594
- Wiring diagram
- Chilling spray (commercially available)

Test Conditions
- The corresponding fuses of Motronic Engine Control Module (ECM) -J220- must be OK
- The parking brake must be applied, otherwise the daytime running lights are switched on.

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







If the specification is not obtained:
- Perform the test according to the following table:







1) If a temperature is indicated that is below the sensors ambient temperature, 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 the specification is obtained:
- Remove Intake Air Temperature (IAT) Sensor -G42-. Re-connect connector.
- Remember the intake air temperature value.
- Spray sensor with commercially available chilling spray and watch temperature value. Temperature value must decrease.
- End diagnosis and switch ignition off.

If the intake air temperature does not drop:
- Replace Intake Air Temperature (IAT) Sensor -G42-.
- Erase DTC memory of ECM. Diagnostic Mode 04 - Erase DTC Memory
- Generate readiness code. Generate Readiness Code

If Display Shows Approx. -40 degrees C:







- Disconnect connector -1 - from Intake Air Temperature (IAT) Sensor -G42- (- 2 -).
- Bridge terminals 1 + 2 of connector using the corresponding adapter cables and observe the indication on display.

If display jumps to approx. 143 degrees C:
- End diagnosis and switch ignition off.
- Replace Intake Air Temperature (IAT) Sensor -G42-.
- Erase DTC memory of ECM. Diagnostic Mode 04 - Erase DTC Memory
- Generate readiness code. Generate Readiness Code

If display stays at approx. -40 degrees C:
- End diagnosis and switch ignition off.
- Check wiring according to wiring diagram.

If Display Shows Approx. 143 degrees C:







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

If display jumps to approx. -40 degrees C:
- End diagnosis and switch ignition off.
- Replace Intake Air Temperature (IAT) Sensor -G42-.
- Erase DTC memory of ECM. Diagnostic Mode 04 - Erase DTC Memory
- Generate readiness code. Generate Readiness Code

If display stays at approx. 143 degrees C:
- End diagnosis and switch ignition off.
- Check wiring according to wiring diagram.

Checking Wiring
- Connect test box to control module wiring harness.
- Check wires between test box and 2-pin connector for open circuit according to wiring diagram.

Terminal 1 + Socket 85
Terminal 2 + Socket 108







Wiring resistance: max. 1.5 Ohms

- Also check wires for short circuit to each other, to vehicle Ground (GND) and to B+.

Specification: Infinity Ohms

If no fault is detected in the wiring:







- Perform a resistance measurement on Intake Air Temperature (IAT) Sensor -G42-.







Area A shows resistance values for temperature range 0 to 50 degrees C, area B shows values for temperature range 50 to 100 degrees C.

Example:
- 30 degrees C is in area A and corresponds to a resistance of 1.5 to 2.0 k Ohms
- 80 degrees C is in area B and corresponds to a resistance of 275 to 375 Ohms

If the specification is not obtained:
- Replace Intake Air Temperature (IAT) Sensor -G42-.
- Erase DTC memory of ECM. Diagnostic Mode 04 - Erase DTC Memory
- Generate readiness code. Generate Readiness Code

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