Air Temperature Sensor ( Ambient / Intake ): Testing and Inspection
Intake Air Temperature (IAT) Sensor, Checking
Only vehicles with engine code BEW
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
- The respective fuses of Diesel-Direct fuel injection system must be OK:
- For vehicles with automatic transmission, selector lever must be in position -P- or -N-.
Function test
- Connect diagnostic tester. Diagnostic Tester, Connecting
- Switch ignition on.
- Under address word 33, select "Diagnostic mode 1: Checking measured values."
- Select measuring value "PID 15: Intake air temperature".
- Check specified value of intake air temperature:
1) If a temperature is indicated which is below 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 a substitute value of approx. 134 degrees C is displayed:
- Check resistance at sensor.
If specified value is not obtained:
- Check sensor.
Checking sensor
- Remove Intake Air Temperature (IAT) Sensor -G42-.
- Re-connect harness connector at Intake Air Temperature (IAT) Sensor -G42-.
- 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 control module for Diesel-Direct fuel injection system, Diagnostic mode 4: Reset/erase diagnostic data. Diagnostic Mode 4: Reset/Erase Diagnostic Data
- Generate readiness code. Monitors, Trips, Drive Cycles and Readiness Codes
Checking resistance at sensor
- Measure resistance at Intake Air Temperature (IAT) Sensor -G42- terminals 1 + 2.
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 k Ohms
- 80 degrees 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 control module for Diesel-Direct fuel injection system, Diagnostic mode 4: Reset/erase diagnostic data. Diagnostic Mode 4: Reset/Erase Diagnostic Data
- Generate readiness code. Monitors, Trips, Drive Cycles and Readiness Codes
If specified value is obtained:
- Connect test box to control module wiring harness, connect test box for wiring test. Test Box, Connecting For Wiring Test
- Connect adapter cable (V.A.G 1598/39-2) to test box (V.A.G 1598/42).
- Check wires between test box and 4-pin connector for open circuit according to wiring diagram.
Terminal 1 + socket 76
Terminal 2 + socket 38
Wire resistance: max. 1.5 Ohms
- Check wires for short circuit to each other, to vehicle Ground (GND) and to B+.
Specified value: Infinite Ohms
If no malfunctions are detected in the wires and the resistance values are OK:
- Replace Diesel Direct Fuel Injection (DFI) Engine Control Module (ECM) -J248-.
- Generate readiness code. Monitors, Trips, Drive Cycles and Readiness Codes