Intake Air Temperature Sensor, Checking

Intake Air Temperature Sensor, Checking

The Intake Air Temperature (IAT) Sensor G42 and the Manifold Absolute Pressure (MAP) Sensor G71 are integrated into one unit and cannot be serviced separately.

Special tools, testers and auxiliary items required
- Multimeter.
- Wiring diagram

Test requirements
- Fuses for engine electronics OK.
- Battery voltage at least 12.5 V.
- The ignition switched off.

Checking function
- Connect the scan tool.
- Switch the ignition on.
- Using the scan tool, check the intake air temperature:

Diagnostic text Specified value
Intake Air Temperature (IAT) approx. ambient air temperature

If the specified value is not obtained:
- End diagnosis and switch the ignition off.

Test procedure
- Perform a preliminary check to verify the customers complaint. General Diagnosis

Start diagnosis







- Remove the rear engine cover - arrows -.

Checking voltage supply







- Disconnect the Intake Air Temperature (IAT) Sensor G42 electrical harness connector - 4 -.

Switch the ignition on







- Using a Multimeter , check the Intake Air Temperature (IAT) Sensor G42 electrical harness connector for voltage.

Intake Air Temperature Specified value
(IAT) Sensor G42 electrical
harness connector
1 to B+ Battery voltage (+)
2 to Ground (GND) Battery voltage (+)
3 to Ground (GND) about 5 V
4 to Ground (GND) Battery voltage (+)

Switch the ignition off

If the specified values are obtained:
- Replace the Intake Air Temperature (IAT) Sensor G42.

If specified values are not obtained:

Checking wiring connections

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

If the manufacturers test box is not being used. Perform the following step.
- Remove the Engine Control Module (ECM) J623.







- 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 terminals for an open circuit.

Intake Air Temperature (IAT) Engine Control Module (ECM)
Sensor G42 electrical harness J623 electrical harness connector
connector terminals terminals or test box sockets
1 40
2 39
3 29
4 44

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).
- Check the electrical harness connector for damage, corrosion, lose or broken terminals.
- If necessary, repair the faulty wiring connection.

If no malfunction is detected in the wiring and if the voltage supply was OK:
- Replace the Engine Control Module (ECM) J623.







- Install the rear engine cover - arrows -.

Final procedures
After repair work, the following work steps must be performed in the following sequence:
1. Check the DTC memory. Diagnostic Mode 03 - Read DTC Memory
2. If necessary, erase the DTC memory. Diagnostic Mode 04 - Erase DTC Memory
3. If the DTC memory was erased, generate readiness code. Monitors, Trips, Drive Cycles and Readiness Codes

- End of diagnosis.