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, Checking: Notes
Observe all safety precautions: SAFETY PRECAUTIONS
View clean working conditions: CLEAN WORKING CONDITIONS
Use only gold-plated terminals when servicing any component with gold-plated electrical harness connector terminals.
For wiring diagrams, component locations, and connector views, Refer to the applicable wiring diagram.
Special tools and workshop equipment required
- Multimeter.
- Wiring diagram.
- Cool spray (commercially available).
Test requirements
- The Engine Control Module (ECM) - J623- 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 was not obtained:
-- Continue test according to the following table:
| Indicated | Cause | Test |
|---|---|---|
| approx. - 40.0° C to - 46° C | Open circuit or short circuit to Battery Voltage | TESTING IF SCAN TOOL DISPLAY IS APPROX. - 40.0° C |
| approx. 140.0° C | Short circuit to Ground (GND) | TESTING IF SCAN TOOL DISPLAY APPROXIMATELY 140.0° C |
If the specified value was obtained:
Checking internal resistance
-- Disconnect the Intake Air Temperature (IAT) Sensor - G42- electrical harness connector -1-.
-- Using a Multimeter, check the Intake Air Temperature (IAT) Sensor - G42- terminals 1 to 2 for resistance.
Use the chart below for the specified values:
Specified values:
| IAT Temperature vs Resistance | ||
| Temp (C) | min. value ohms | max. value ohms |
| - 40 | 36816 | 43714 |
| - 35 | 28840 | 33978 |
| - 25 | 17680 | 20530 |
| - 15 | 10940 | 12534 |
| - 5 | 6897 | 7804 |
| 0 | 5535 | 6226 |
| 5 | 4443 | 4970 |
| 15 | 2923 | 3235 |
| 25 | 1978 | 2167 |
| 35 | 1369 | 1486 |
| 45 | 965 | 1039 |
| 55 | 692 | 738 |
| 65 | 503 | 533 |
| 75 | 372 | 392 |
| 85 | 279 | 292 |
If any of the specified value's were not obtained:
-- Replace the Intake Air Temperature (IAT) Sensor - G42-. Refer to appropriate service information.
-- Go to Final procedures
If the specified values were obtained:
-- Replace the Motronic Engine Control Module (ECM) -J623 -. Refer to appropriate service information.
-- Go to Final procedures
Use the Manual With the Right Hardware
Pair factory procedures with proven DIY tools so the instructions are easier to execute.
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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.
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