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.G 1526 multimeter or V.A.G 1715 multimeter
- V.A.G 1594 connector test kit
- Wiring diagram
- Chilling spray (commercially available)

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: Check measured values."
- Select measuring value "PID 15: Intake air temperature".
- Check specified value of intake air temperature:







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 Fuel Temperature 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 kohms
- 80 degrees C is in range B and corresponds to a resistance of 275 to 375 Ohms

If specified value is not obtained:
- Replace Fuel Temperature 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