Intake Air Temperature Sensor, Checking
Diagnostic Procedures
Intake Air Temperature Sensor, Checking
NO MAF
• The Manifold Absolute Pressure sensor and the Intake Air Temperature sensor are combined as a unit and are serviced as an assembly.
• Use only gold-plated terminals when servicing terminals in the electrical harness connector of the MAP / IAT sensor (G71 / 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.
If the specified value was Not obtained:
Checking internal resistance
- Disconnect the MAP / IAT sensor (G71/G42) electrical harness connector.
- Using a multimeter, check the MAP / IAT sensor ( G71/G42) terminals 1 to 2 for resistance.
Use the chart below for the specified values:
Specified values:
If the specified value was Not obtained:
- Replace the MAP / IAT sensor (G71 / G42).
If the specified value was obtained:
- Continue the test according to the following table:
Checking Component and wiring
- Disconnect the MAP / IAT sensor (G71 / G42) electrical harness connector - 1 -.
- Using a multimeter, connect the positive lead to the MAP / IAT sensor (G71 / G42) harness connector terminal 2 and the negative lead to an engine ground.
Specified value: 4.30 V to 4.90 V
If the specified value was Not obtained:
- Check the wiring for an open, high resistance or short to ground.
- Check the electrical 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) (J623). 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 MAP / IAT sensor (G71 / 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 electrical 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 MAP / IAT sensor (G71 / G42).
°Testing if display is - 40 C :
- Disconnect the MAP / IAT sensor (G71 / G42) electrical harness connector.
- Using a jumper wire, connect the MAF / IAT sensor (G71 / G42) electrical 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 MAP / IAT sensor (G71 / 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) ( J623). Refer to the repair information.
- Using a multimeter, check the MAP / IAT sensor ( G71 / G42) electrical harness connector terminal 2 to the Motronic Engine Control Module (ECM) (J623) electrical harness connector T60 terminal 42 for an open circuit or a short to voltage, refer to the wiring diagram.
- Using a multimeter, check the MAP / IAT sensor ( G71 / G42) electrical harness connector terminal 1 to the Motronic Engine Control Module (ECM) (J623) electrical harness connector T60 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 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:
- Replace the Motronic Engine Control Module (ECM) (J623). Refer to the repair information.
°Testing if display near 140 C:
- Disconnect the MAP / IAT sensor (G71 / 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 MAP / IAT sensor (G71 / G42).
If the indication remains at approx. 140 °C:
Checking wiring
- Remove the Motronic Engine Control Module (ECM) ( J623). Refer to the repair information
- Disconnect the T60 connector.
- Using a multimeter, check for continuity between the MAP / IAT sensor (G71 / G42) electrical harness connector terminal 2 to an engine ground, refer to the wiring diagram.
- Using a multimeter, check for continuity between the MAP / IAT sensor (G71 / G42) electrical harness connector terminal 2 to terminal 1, refer to the wiring diagram.
Specified value: OL or no continuity.
- Repair the short to ground.
If no malfunction is detected in the wiring:
- Replace the Motronic Engine Control Module (ECM) (J623). 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 ] Scan Tool Testing and Procedures.
2. If necessary, erase the DTC memory. Refer to => [ Diagnostic Mode 04 - Erase DTC Memory ] Scan Tool Testing and Procedures.
3. If the DTC memory was erased, generate readiness code. Refer to => [ Readiness Code ] Monitors, Trips, Drive Cycles and Readiness Codes.