Intake Air Temperature Sensor, Checking

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.

• Cool spray (commercially available).

Test requirements

• The Engine Control Module (ECM) ( J623) 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:

- Continue the test according to the following table:





If the specified values are obtained:

- Remove engine cover - arrows -.





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

- Spray the Intake Air Temperature (IAT) Sensor ( G42) with a commercially available cool spray while observing the temperature value on the scan tool.

The temperature value must decrease.

- End diagnosis and switch the ignition off.

If the intake air temperature does not decrease:

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

If the intake air temperature does decrease:

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) terminals 1 to 2 for resistance.





Use the chart below for the specified values:

• Area A: Resistance values 0 to 50° C.

• Area B: Resistance values 50 to 100° C.

Specified values:





Read-out examples:

• Range A, 30° C equals a resistance of 1.5 to 2.0 kohms

• Range B, 80° C equals a resistance of 275 to 375ohms

If any of the specified values are not obtained:

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

°°Testing if display approx. -40 C or approx. -46 C:

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





- Using a jumper wire, connect the Intake Air Temperature (IAT) Sensor (G42) electrical harness connector terminals 1 to 2.

- Check the value indicated on the scan tool display.





If indication jumps to approx. 140° C:

- End diagnosis and switch ignition off.

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

If indication remains at approx. -40° C or -46° C:

°Testing if display approx. 140 C:

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





If indication jumps to approx. -40° C or -46° C:

- End diagnosis and switch ignition off.

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

If the indication remains at approx. 140° C:

Checking wiring

If the manufacturers test box is being used. Perform the following step.

- Install the test box. Refer to Fuel Injection and Ignition Repair Information

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

- Remove the Engine Control Module (ECM) (J623). Refer to => [ Engine Control Module, Replacing ] Service and Repair.

- Using a Multimeter, check the Intake Air Temperature (IAT) Sensor (G42 ) electrical harness connector terminals to the Engine Control Module (ECM) ( J623) electrical harness connector T60 terminals for resistance.









Specified value: 1.5 ohms Max.

If the specification was not obtained:

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

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

- If necessary, repair the faulty wiring connection.

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 ] Monitors, Trips, Drive Cycles and Readiness Codes.

- End diagnosis.

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

- Replace the Engine Control Module (ECM) (J623 ). Refer to => [ Engine Control Module, Replacing ] Service and Repair.

- Assembly is performed in the reverse of the removal.

Final procedures

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

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

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

3. If the DTC memory was erased, generate readiness code. => [ Readiness Code ] Monitors, Trips, Drive Cycles and Readiness Codes.

End of diagnosis