Air Temperature Sensor ( Ambient / Intake ): Testing and Inspection

Intake Air Temperature Sensor, Checking

• Use only gold-plated terminals when servicing terminals in the electrical harness connector of the Intake Air Temperature (IAT) Sensor (G42).

Special tools, testers and auxiliary items required

• Multimeter.

• Wiring diagram.

Test requirements

• The Diesel Direct Fuel Injection (DFI) Engine Control Module (ECM) (J248) fuses OK.

• Battery voltage at least 12.5 volts.

• All electrical consumers such as, lights and rear window defroster, switched off.

• Vehicles with automatic transmission, shift selector lever into position "P" or "N".

• A/C switched off.

• Ground (GND) connections between engine/transmission/chassis OK.

• Ignition switched off.

Test procedure

- Perform a preliminary check to verify the customers complaint. Refer to => [ General Diagnosis ] General Diagnosis.

Start diagnosis

- Connect the scan tool.

- Switch the ignition on.

- Using the scan tool, check the intake air temperature:





If the specified value is not obtained:

Checking internal resistance

- Disconnect the Intake Air Temperature (IAT) Sensor (G42) electrical harness connector - 1 -.





- Using a multimeter, check the Intake Air Temperature (IAT) Sensor (G42) - 2 - terminals 1 to 2 for resistance.

Use the chart below for the specified values:





• Area A: Resistance values 0 to 50° C (32° - 122° F).

• Area B: Resistance values 50 to 100° C (122° - 212° F).

Examples:

• Range A, 30° C (86° F) equals a resistance of 1500 to 2000 ohms

• Range B, 80° C (176° F) equals a resistance of 275 to 375ohms

If any of the specified values are not obtained:

- Replace the Intake Air Temperature (IAT) Sensor (G42).

If the specified values were obtained:

Checking wiring

If the manufacturers test box is being used, perform the following step.

- Install the test box. Refer to => [ 68-Pin Test Box Adapter, VAG1598/19, Installing ] Diesel Direct Fuel Injection ECM, Checking.

If the manufacturers test box is not being used, perform the following step.

- Remove the Diesel Direct Fuel Injection (DFI) Engine Control Module (ECM) (J248). Refer to => [ Diesel Direct Fuel Injection ECM, Replacing ] Diesel Direct Fuel Injection ECM, Checking.

- Using a Multimeter, check the Intake Air Temperature (IAT) Sensor (G42) electrical harness connector terminals to the Diesel Direct Fuel Injection (DFI) Engine Control Module (ECM) (J248) electrical harness connector T94 terminals for resistance.









Specified value: 1.5 ohms Max.

If the specification was not obtained:

- Check the wiring for a short circuit to each other, Battery (+), and Ground (GND).

- If necessary, repair the faulty wiring connection.

- Check the electrical harness connector for damage, corrosion, loose or broken terminals.

If no malfunction is detected in the wiring:

- Erase the DTC memory. Refer to => [ Diagnostic Mode 04 - Erase DTC Memory ] Diagnostic Mode 04 - Erase DTC Memory.

- Perform a road test to verify repair.

If the DTC does not return:

Repair complete, Generate readiness code. Refer to => [ Readiness Code ] Readiness Code.

- End diagnosis.

If the DTC does return and no malfunction is detected in the wiring and the voltage supply was not OK:

- Replace the Diesel Direct Fuel Injection (DFI) Engine Control Module (ECM) (J248). Refer to => [ Diesel Direct Fuel Injection ECM, Replacing ] Diesel Direct Fuel Injection ECM, Checking.

- Assembly is performed in the reverse of the removal.

Final procedures

After the repair work, the following work steps must be performed in the following sequence:

1. Check the DTC memory. Refer to => [ Diagnostic Mode 03 - Read DTC Memory ] Diagnostic Mode 03 - Read DTC Memory.

2. If necessary, erase the DTC memory. Refer to => [ Diagnostic Mode 04 - Erase DTC Memory ] Diagnostic Mode 04 - Erase DTC Memory.

3. If the DTC memory was erased, generate readiness code. Refer to => [ Readiness Code ] Readiness Code.