Intake Air Temperature Sensor, Checking

Diagnostic Procedures

Intake Air Temperature Sensor, Checking

• The Mass Air Flow sensor and the Intake Air Temperature sensor are combined as a unit.

• Use only gold-plated terminals when servicing terminals in the electrical harness connector of the MAF / IAT sensor (G70 / G42).

Special tools, testers and auxiliary items required

• Multimeter.

• Wiring diagram.

Test procedure

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

Start diagnosis

- Connect the scan tool.

- Engine must be at Room Temperature.

- Switch the ignition ON.

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





If the specified value was obtained:

- Fault is intermittent. Check for proper connection, damaged wiring or loose terminals.

- Switch the ignition OFF.

If the specified value was Not obtained:

Checking internal resistance

- Disconnect the MAF / IAT sensor (G70 / G42) electrical harness connector.

- Using a multimeter, check the MAF / IAT sensor ( G70 / G42) terminals 1 to 2 for resistance.

Use the chart below for the specified values:

Specified values:





If the specified value in the chart was Not obtained:

- Replace the MAF / IAT sensor (G70 / G42).

If the specified value was obtained:

- Continue the test according to the following table:





Checking Component and wiring

- Disconnect the MAF / IAT sensor (G70 / G42) electrical harness connector.

- Using a multimeter, connect the positive lead to the MAF / IAT sensor (G70 / G42) harness connector terminal 2 and the negative lead to an engine ground.

Specified value: Near 5 V

If the specified value was Not obtained:

- Check the wiring for an open, high resistance or short to ground.

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

- If necessary, repair the faulty wiring or connection.

If voltage was not present and no malfunction is detected in the signal circuit:

- Replace the Motronic Engine Control Module (ECM) (J220). Refer to the Repair Information.

If the specified value was obtained:

- Using a multimeter, connect the positive lead to Battery + and the negative lead to the MAF / IAT sensor (G70 / G42) harness connector terminal 1.

Specified value: Battery voltage.

If the specified value was Not obtained:

- Check the ground circuit for an open or high resistance.

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

- If necessary, repair the faulty wire or connection.

If the specified value was obtained:

- Replace the MAF / IAT sensor (G70 / G42).

°Testing if display is - 40 C :

- Disconnect the MAF / IAT sensor (G70 / G42) electrical harness connector.

- Using a jumper wire, connect the MAF / IAT sensor (G70 / G42) harness connector terminals 1 to 2.

- Check the value indicated on the scan tool display.

- Switch ignition OFF.

If indication jumps to approx. 140 °C:

- Replace the MAF / IAT sensor (G70 / G42).

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

Checking wiring

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 Motronic Engine Control Module (ECM) ( J220). Refer to the Repair Information.

- Using a multimeter, check the MAF / IAT sensor ( G70 / G42) harness connector terminal 2 to the Motronic Engine Control Module (ECM) (J220) electrical harness connector T121 terminal 42 for an open circuit or a short to voltage, refer to the wiring diagram.

- Using a multimeter, check the MAF / IAT sensor ( G70 / G42) harness connector terminal 1 to the Motronic Engine Control Module (ECM) (J220) electrical harness connector T121 terminal 13 for an open, high resistance or a short to voltage, refer to the wiring diagram.

Specified resistance: 1.5 ohms Max.

If the specified value was Not obtained:

- Check the wiring for an open, high resistance or short circuit to Battery (+).

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

- If necessary, repair the faulty wiring connection.

If no malfunction is detected in the wiring:

- Replace the Motronic Engine Control Module (ECM) (J220). Refer to the Repair Information.

°Testing if display near 140 C:

- Disconnect the MAF / IAT sensor (G70 / G42) electrical harness connector.

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

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

- Switch ignition OFF.

- Replace the MAF / IAT sensor (G70 / G42).

If the indication remains at approx. 140 °C:

Checking wiring

- Remove the Motronic Engine Control Module (ECM) ( J220). Refer to the Repair Information.

- Disconnect the T60 connector.

- Using a multimeter, check for continuity between the MAF / IAT sensor (G70 / G42) harness connector terminal 2 to an engine ground, refer to the wiring diagram.

- Using a multimeter, check for continuity between the MAF / IAT sensor (G70 / G42) harness connector terminal 2 to terminal 1, refer to the wiring diagram.

Specified value: OL or no continuity.

If the specified value was Not obtained:

- Repair the short to ground in the circuit.

If the specified value was obtained:

- Replace the Motronic Engine Control Module (ECM) (J220). Refer to the Repair Information.

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 Modes 01 - 09.

2. If necessary, erase the DTC memory. Refer to => [ Diagnostic Mode 04 - Erase DTC Memory ] Diagnostic Modes 01 - 09.

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