Intake Air Temperature Sensor, Checking

Special tools and workshop equipment required 

• Multimeter.
• Wiring diagram.

Test requirements 

• The Diesel Direct Fuel Injection (DFI) Engine Control Module (ECM) -J248- 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:

Checking internal resistance 

-- Disconnect the Intake Air Temperature (IAT) Sensor -G72- electrical harness connector -1-.

-- Using a multimeter, check the Intake Air Temperature (IAT) Sensor -G72- -2- terminals 1 to 2 for resistance.

Use the chart below for the specified values:

• Area A: Resistance values 0 to 50° C (32° - 122° F).
• Area B: Resistance values 50 to 100° C (122° - 212° F).

Examples: 

• Range A, 30° C (86° F) equals a resistance of 1500 to 2000 Ω
• Range B, 80° C (176° F) equals a resistance of 275 to 375Ω

If any of the specified values are not obtained:

-- Replace the Intake Air Temperature (IAT) Sensor -G72-.

If the specified values were obtained:

Checking wiring 

If the manufacturers test box is being used, perform the following step.

-- Install the test box. Refer to 68 PIN TEST BOX ADAPTER, INSTALLING .

If the manufacturers test box is not being used, perform the following step.

-- Remove the Diesel Direct Fuel Injection (DFI) Engine Control Module (ECM) -J248-. Refer to ENGINE CONTROL MODULE, REPLACING .

-- Using a Multimeter --, check the Intake Air Temperature (IAT) Sensor -G72- electrical harness connector terminals to the Diesel Direct Fuel Injection (DFI) Engine Control Module (ECM) -J248- electrical harness connector T94 terminals for resistance.

Intake Air Temperature (IAT) Sensor -G72- electrical harness connector terminals	Diesel Direct Fuel Injection (DFI) Engine Control Module (ECM) -J248- electrical harness connector T94 terminals or test box socket
1	76
2	38

Specified value: 1.5 Ω Max.

If the specification was not obtained:

-- Check the wiring for a short circuit to each other, Battery (+), and Ground (GND).

-- If necessary, repair the faulty wiring connection.

-- Check the electrical harness connector for damage, corrosion, loose or broken terminals.

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:

Repair complete, Generate readiness code. Refer to READINESS CODE .

-- End diagnosis.

If the DTC does return and no malfunction is detected in the wiring and the voltage supply was not OK:

-- Replace the Diesel Direct Fuel Injection (DFI) Engine Control Module (ECM) -J248-. Refer to ENGINE CONTROL MODULE, REPLACING .

-- Assembly is performed in the reverse of the removal.

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 .
2. If necessary, erase the DTC memory. Refer to DIAGNOSTIC MODE 04 - ERASE DTC MEMORY .
3. If the DTC memory was erased, generate readiness code. Refer to READINESS CODE .

End of diagnosis