Intake Air Temperature (IAT) Sensor, Checking
Intake Air Temperature (IAT) Sensor, Checking
NOTE: Use only gold-plated terminals when servicing terminals in harness connector.
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:
- Battery voltage must be at least 11.5 volts.
- For vehicles with automatic transmission, selector lever must be in position -P- or -N-.
- Parking brake must be engaged.
- Ground (GND) connections between engine and chassis must be OK.
- Ignition is switched off.
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 Cis displayed:
- Check resistance at Intake Air Temperature (IAT) Sensor -G42-.
If specified value is not obtained:
- Check Intake Air Temperature (IAT) Sensor -G42-.
Checking sensor
- Disconnect 4-pin connector from Intake Air Temperature (IAT) Sensor -G42- with Charge Air Pressure Sensor -G31- (arrow).
- Remove Intake Air Temperature (IAT) Sensor -G42-.
- Re-connect harness connector at Intake Air Temperature (IAT) Sensor -G42-.
- Remember the 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- with Charge Air Pressure Sensor -G31-.
- Erase DTC memory of Engine Control Module (ECM), 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 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 Intake Air Temperature (IAT) Sensor -G42- with Charge Air Pressure Sensor -G31-.
- Erase DTC memory of Engine Control Module (ECM), 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:
- Check wires to Engine Control Module (ECM) according to wiring diagram.
Check wires to control module
- Connect test box (1598/42) to Diesel Direct Fuel Injection (DFI) Engine Control Module (ECM) -J248- wiring harness using adapter cable (V.A.G 1598/39-2), connecting test box for wiring test. Test Box, Connecting For Wiring Test
- 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-.