IAT Sensor, Checking
IAT Sensor, Checking
• Use only gold-plated terminals when servicing terminals in the electrical harness connector of the IAT sensor (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:
- Turn the ignition switch OFF.
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 IAT sensor (G42) electrical harness connector.
- Using a multimeter, check the IAT sensor (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 IAT sensor (G42) Refer to the repair information.
- If the specified values are obtained continue the test according to the following table:
°°Testing if display approx. - 40 C or approx. - 46 C:
- Disconnect the IAT sensor (G42) electrical harness connector.
- Using a jumper wire, connect the IAT sensor (G42) electrical harness connector terminals 1 to 2.
- Turn the ignition switch ON.
- Check the value indicated on the scan tool display.
If indication jumps to approx. 140 °C:
- Switch ignition OFF.
- Replace the IAT sensor (G42). Refer to the repair information.
If indication remains at approx. - 40 °C to - 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 IAT sensor (G42). Refer to the repair information.
- Using a multimeter, check the IAT sensor (G42) electrical harness connector terminal 1 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.
Specified value: 1.5 ohms Max.
If the specified value was Not obtained:
- Check the wiring for an open, high resistance or short circuit to Battery positive.
- Check the electrical harness connector for damage, corrosion, loose or broken terminals.
- If necessary, repair the faulty wiring connection.
If the specified value was obtained:
- Using a multimeter, check terminal 2 of the IAT sensor to the Motronic Engine Control Module (ECM) (J623) electrical harness connector T60 terminal 14 for an open circuit or short.
Specified value: 1.5 ohms Max
If the specified value was Not obtained:
- Check the wiring for an open circuit or high resistance.
- 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 circuit:
- Replace the Motronic Engine Control Module (ECM) (J623). Refer to the repair information.
°Testing if display approx. 140 C:
- Disconnect the IAT sensor (G42) electrical harness connector.
- Turn the ignition switch ON.
- Check the value indicated on the scan tool display.
If indication jumps to approx. - 40 °C or - 46 °C:
- Switch ignition OFF.
- Replace the IAT sensor (G42). Refer to the repair information.
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.
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.
- Disconnect the ECM harness.
- Using a multimeter, check the IAT sensor (G42) electrical harness connector terminal 1 to engine ground for continuity.
Specified value: OL or No continuity.
If the specified value was Not obtained:
- Check the wiring for a short circuit to Ground.
- If necessary, repair the faulty wiring connection.
- Check the electrical harness connector for damage, corrosion, loose or broken terminals.
If the specified value was obtained:
- Check the IAT signal circuit from terminal 1 of the IAT to the Motronic Engine Control Module (ECM) (J623) electrical harness connector T60 terminal 42 of the ECM harness for resistance.
If no malfunction is found in 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 ] 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 ] Monitors, Trips, Drive Cycles and Readiness Codes.