How To Test: P0113 OBD II Trouble Code (GM 3.8L)

Troubleshooting P0113: Intake Air Temperature Circuit High Input

START HERE: Troubleshooting a P0113 isn't hard and I'll summarize what you'll be doing in this section.

Basically, you'll need to do 3 specific things:

1. Verify that the temperature that the IAT sensor is reporting is in the extreme cold (-30 °F or less).
   • You need to confirm that the problem is present before performing all of the tests in this tutorial.
   • TEST 1: Checking The Intake Air Temperature Value.
2. Perform a wiggle test to see if the problem is in the IAT sensor connector's wiring.
   • This test will confirm that the problem is not in the IAT sensor's wiring.
   • TEST 2: Wiggle Testing the IAT Sensor's Wiring.
3. Making sure that the PCM can react to a low voltage drop.
   • What you'll do here is to use a jumper wire to jumper the IAT sensor's connector and then see if the PCM reports a temperature around 300 °F. This will confirm that there are no shorts in the wiring and that the PCM is good.
   • TEST 3: Jumpering the IAT Sensor Circuit.

TEST 1: Checking The Intake Air Temperature Value

The very first that you and I need to do, is to see what temperature the intake air temperature (IAT) sensor is reporting to the PCM (Powertrain Control Module = Fuel Injection Computer).

Specifically, we need to confirm that the PCM is really seeing an absurd low temp of minus 30 °F (-30 °F).

The fastest and easiest way to this is using a scan tool with Live Data capability and this is exactly how we're gonna' test it.

Now, it's possible to check the IAT sensor without a scan tool. How? By measuring the resistance of the IAT sensor and them comparing them to the actual ambient temperature that your car or mini-van is in. To see the Resistance/Temperature Chart, go here: Intake Air Temp (IAT) Temperature/Resistance Chart.

If you don't have a scan tool and you need to buy one, check out my Actron CP9580 Scan Tool Review.

IMPORTANT: The engine should be completely cold before you start this test.

OK, this is what you need to do:

1. 1

   Connect your scan tool to your 3.8L GM equipped car or mini-van and turn the key to the on position (you don't need to start the engine).

2. 2

   Once the scan tool has powered up, go to its Live Data mode.

3. 3

   Scroll down to the PID labeled IAT (°F)

   1. In case you're wondering what the acronym PID stands for, it's: Parameter Identification.
4. 4

   The scan tool should register a temperature that should be within ±10 °F of ambient temperature (if all is normal)

   1. So let's say that it's 50 °F outside, then the IAT sensor PID should register something between 40 to 60 °F.
5. 5

   Now, since you're here because you have an IAT sensor diagnostic trouble code (DTC), more than likely you'll see one of the following:

   1. - 30 to -40 °F (that's negative 30 to 40 °F).
   2. OR 300 °F.

Let's interpret your test results:

CASE 1: Your scan tool shows a -30 to -40 °F reading. This confirms that there is a problem with the intake air temperature (IAT) sensor.

This test result also confirms that the diagnostic trouble code P0113 (IAT Sensor Circuit High Voltage), that was stored in the PCM's memory is telling you the truth.

The most likely cause will be that the IAT sensor circuit is ‘open’. By ‘open’ I mean that there's a break in one or both of the wires that feed the intake air temperature (IAT) sensor or that the IAT sensor itself is fried and causing an extremely high resistance.

The next test will help you to further narrow down the problem. Go to: TEST 2: Wiggle Testing the IAT Sensor's Wiring.

CASE 2: Your scan tool shows a 300+ °F reading. This confirms that you do have a problem with the intake air temperature (IAT) sensor or its circuits.

Seeing a temperature of 300 °F indicates one of two things, either that the IAT sensor has shorted together inside or the IAT sensor connector's wires are shorted together. You'll also see a diagnostic trouble code P0112 (IAT Sensor Circuit Low Voltage) stored in the PCM's memory.

CASE 3: Your scan tool shows a temperature reading that's ±10 °F of ambient temperature- This tells you that at the moment the IAT sensor and its circuits are OK.

But, since your scan tool retrieved a DTC P0113 the problem may just be hiding at the moment, I recommend clearing the diagnostic trouble code (DTC) and road testing your vehicle to see if the code comes back.

If the P0113 DTC does come back, repeat this test once more.