How To Test The Intake Air Temp (IAT) Sensor (GM 3.5L)

TEST 5: Jumpering The IAT Sensor Circuits

So far, you have done the following: confirmed that you have a Diagnostic Trouble Code (DTC) P0113: Intake Air Temperature (IAT) Sensor Circuit High Voltage.

Also, you've done TEST 1, where you've confirmed that the IAT Sensor PID (on your scan tool) is registering a temperature of -30 to -40 °F.

The next step, is to use a jumper wire and jumper the two IAT sensor wires together. These two are the ones labeled with the letters D and E of the MAF sensor connector in the image viewer.

If all is OK in the wiring and in the PCM, after jumpering these two wires together, the PCM will read a temperature of 300 °F and will set a DTC P0112: Intake Air Temperature (IAT) Sensor Circuit Low Voltage.

OK, here's what you'll need to do:

1. Keep your scan tool connected to your vehicle.
2. Disconnect the mass air flow (MAF) sensor from its connector.
3. Locate the wires identified with the letter D and letter E.
   • Wire D is the Tan wire.
   • Wire E is the Black w/ White stripe wire.
4. Jumper these 2 wires together with a jumper wire.
5. Turn the key to the ON position (RUN position)
6. Let the scan tool power up and go to Live Data mode.
   • Scroll down to the IAT Sensor PID (see photo 3 of 3).
7. Your scan tool should now read 300 °F for the intake air temperature (IAT) sensor reading.
   • You'll also see DTC P0112.

Let's analyze your test results:

CASE 1: The scan tool registered 300 °F - This test result tells you that the wiring between the PCM and MAF sensor connector is OK and that the PCM is not fried.

The next step is to check the internal resistance of the intake air temperature sensor to see if it has an ‘open’.

For this test, go to: TEST 7: IAT Sensor Resistance Test (P0113).

CASE 2: The scan tool DID NOT register 300 °F. Make sure that you're testing the correct wires, that your connections are OK, and repeat the test.

Then this tells you that you have a problem in the wiring between the IAT Sensor and the PCM or that the PCM is fried (although a bad PCM is rare).

The next step for you, is to make sure that the IAT sensor is getting power and Ground from its two wires. For this test, go to: TEST 8: 5 Volt Reference Circuit.

TEST 6: IAT Sensor Resistance Test (P0112)

In this test step, you're gonna check the resistance of the intake air temperature (IAT) sensor with your multimeter in Ohms mode.

This will check to see if the IAT sensor has shorted together inside the MAF sensor and causing a resistance between 0 and 47 Ohms.

If the intake air temperature (IAT) sensor is producing a resistance between 0 and 47 Ωs., then the PCM will output a temperature of 300 °F and set diagnostic trouble code (DTC) P0112: Intake Air Temperature (IAT) Sensor Circuit Low Voltage.

OK, to get this test going, this is what you need to do:

1. Disconnect the MAF sensor connector and remove the MAF sensor.
   • You don't have to remove the MAF sensor for this test, but I personally thinks it makes it a little easier to do this test with the MAF sensor removed.
2. On the MAF sensor, locate the pins that correspond to the letters D and E of the MAF connector.
3. With your multimeter in Ohms (Ω) mode:
   • Measure the resistance of the intake air temperature (IAT) sensor.

Let's interpret your test results:

CASE 1: The multimeter recorded 0 to 47 Ohms- This tells you that the intake air temperature (IAT) sensor inside the mass air flow (MAF) sensor is bad.

Since the IAT sensor is part of the MAF sensor, you'll need to replace the entire MAF sensor to solve the P0112 Diagnostic Trouble Code.

CASE 2: The multimeter DID NOT record 0 to 47 Ohms- So far so good, but you're not out of the woods yet.

The next step is to check the resistance you're getting to the temperature versus resistance chart in the next page.

The resistance should correspond to the outside temperature (ambient temperature) of your area. For this info, go to: IAT Sensor Temperature/Resistance Chart.