Intake Air Temperature Sensor, Checking
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.
The Intake Air Temperature (IAT) Sensor -G42- is an integral part of Mass Air Flow (MAF) Sensor -G70-. Replacing either component requires replacement of the entire assembly.
Special tools and workshop equipment required
- multimeter.
- Wiring diagram.
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 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+) | INTAKE AIR TEMPERATURE SENSOR, CHECKING |
| approx. 140° C | Short circuit to Ground (GND) | INTAKE AIR TEMPERATURE SENSOR, CHECKING |
If the specified values are obtained:
-- Remove engine cover. Refer to the appropriate service manual.
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 | 31811 | 37560 |
| - 35 | 22941 | 26863 |
| - 25 | 12415 | 14289 |
| - 15 | 6958 | 7880 |
| - 5 | 4036 | 4495 |
| 0 | 3120 | 3442 |
| 5 | 2422 | 2655 |
| 15 | 1519 | 1623 |
| 25 | 968 | 1031 |
| 35 | 629 | 676 |
| 45 | 419 | 455 |
| 55 | 286 | 314 |
| 65 | 195 | 217 |
| 75 | 136 | 155 |
If any of the specified values are not obtained:
-- Replace the Intake Air Temperature (IAT) Sensor -G42-. Refer to the appropriate service manual.
INTAKE AIR TEMPERATURE SENSOR, CHECKING Testing if display approx. -40° C or approx. -46° C:
-- Disconnect the Intake Air Temperature (IAT) Sensor -G42- electrical harness connector -1-.
-- Using a jumper wire, connect the Intake Air Temperature (IAT) Sensor -G42- electrical harness connector terminals 1 to 2.
-- Check the value indicated on the scan tool display.
If indication jumps to approx. 140° C:
-- End diagnosis and switch ignition off.
-- Replace the Intake Air Temperature (IAT) Sensor -G42-. Refer to appropriate service manual.
If indication remains at approx. -40° C or -46° C:
Refer to INTAKE AIR TEMPERATURE SENSOR, CHECKING .
-- Disconnect the Intake Air Temperature (IAT) Sensor -G42- electrical harness connector -1-.
If indication jumps to approx. -40° C or -46° C:
-- End diagnosis and switch ignition off.
-- Replace the Intake Air Temperature (IAT) Sensor -G42 -. Refer to appropriate service manual.
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 Engine Control Module (ECM) -J623-. Refer to appropriate service manual.
-- Using a Multimeter --, check the Intake Air Temperature (IAT) Sensor -G42 - electrical harness connector terminals to the Engine Control Module (ECM) -J623- electrical harness connector T94 terminals for resistance.
| Intake Air Temperature (IAT) Sensor -G42 - electrical harness connector terminals | Engine Control Module (ECM) -J623- electrical harness connector T94 terminals or test box socket |
|---|---|
| 4 | 64 |
| 5 | Fuse S11 |
Specified value: 1.5 Ω Max.
If the specification was not obtained:
-- Check the wiring for an open circuit, a short circuit to Battery (+), or an open circuit.
-- 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:
-- Erase the DTC memory. Refer to DIAGNOSTIC MODE 04 - ERASE DTC MEMORY .
-- Perform a road test to verify repair.
If the DTC does not return:
Generate readiness code. Refer to READINESS CODE .
If the DTC does return and no malfunction is detected in the wiring and the voltage supply was not OK:
-- Replace the Engine Control Module (ECM) -J623-. Refer to appropriate service manual.
Final procedures
After repair work, the following work steps must be performed in the mentioned sequence:
- Check the DTC memory. DIAGNOSTIC MODE 03 - READ DTC MEMORY .
- If necessary, erase the DTC memory. DIAGNOSTIC MODE 04 - ERASE DTC MEMORY .
- If the DTC memory was erased, generate readiness code. READINESS CODE .