Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Intake Air Temperature Sensor 2, Checking: Notes
Use only gold-plated terminals when servicing terminals in the electrical harness connector of the Intake Air Temperature (IAT) Sensor 2 -G299-.
Special tools and workshop equipment required
- Multimeter.
- Wiring diagram.
- Cool spray (commercially available).
Test requirements
- The Motronic Engine Control Module (ECM) - J220- 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 PRELIMINARY CHECK
Start diagnosis
-- 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:
-- Continue the test according to the following table:
| Indicated | Cause | Test |
|---|---|---|
| approx. -40° C or approx. -46° C | Open circuit or short circuit to (B+) | TESTING IF DISPLAY APPROX. -40 °C OR APPROX. -46 C OR APPROX. -46 °C: |
| approx. 140° C | Short circuit to Ground (GND) | TESTING IF DISPLAY APPROX. 140 °C: |
If the specified values are obtained:
-- Remove the Intake Air Temperature (IAT) Sensor -G42-. Refer to Repair information.
-- Spray the Intake Air Temperature (IAT) Sensor 2 -G299- 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 2 -G299-. Refer to Repair information.
If the intake air temperature does decrease:
Checking internal resistance
-- Disconnect the Intake Air Temperature (IAT) Sensor 2 -G299- electrical harness connector -arrow-.
-- Using a Multimeter, check the Intake Air Temperature (IAT) Sensor 2 -G299- 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 kΩ
- Range B, 80° C equals a resistance of 275 to 375Ω
If any of the specified values are not obtained:
-- Replace the Intake Air Temperature (IAT) Sensor 2 -G299-. Refer to Repair information.
NO RELATED
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.