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

TEST 2: Wiggle Testing The IAT Sensor's Wiring

So far you have confirmed, via your scan tool, that a diagnostic trouble code P0113 (IAT Sensor Circuit High Voltage) registered in the PCM's memory.

You have also confirmed, via your scan tool's Live Data mode, that your vehicle's PCM is reading an intake air temperature (IAT) of -30 to -40 °F.

In this test step, you're gonna' wiggle the IAT sensor connector's 2 wires, while you observe your scan tool to see if this has an effect on your IAT sensor temperature reading.

What's the purpose of this wiggle test? It's to see if wiggling the IAT sensor's wires causes the temperature reading of -30 °F to go back to reading a normal temperature.

OK, this is what you need to do:

1. 1

   Connect your scan tool and get to its Live Data mode.

2. 2

   Scroll down to the PID for the IAT sensor.

   1. -30 to -40 °F temperature reading should still be present.
3. 3

   Now, have a helper (or yourself) gently wiggle the IAT sensor connector's 2 wires as you keep your eyeballs on the IAT sensor PID on your scan tool.

4. 4

   If the IAT sensor connector is bad, you'll see the IAT sensor reading go from -30 to -40 °F to a normal temperature.

   1. By a normal temperature, I mean something that resembles the temperature of the outside air of the area you're in.

Let's interpret your test results:

CASE 1: Wiggling the IAT sensor connector's wires caused the temperature to change. This test result tells you that there's a problem with the connector or a problem in one of the 2 wires that attach to it.

You need to carefully inspect the connector and the 2 wires and replace and/or repair what is damaged or shorted.

To give you some more specifics: Gently wiggling the IAT sensor connector's 2 wires should have no effect on the IAT sensor reading displayed on the scan tool, unless the connector is bad or one of the wires has an ‘open’. Since wiggling the connector did have an effect, you now know that replacing the IAT sensor connector or repairing the problem in the wires will solve the IAT sensor and P0113 Code problem.

CASE 2: Wiggling the IAT sensor connector's wires DID NOT cause the temperature to change. This tells you that the IAT sensor connector and its wires are OK.

In most cases, this test result also tells you that the IAT sensor is the one that's malfunctioned and needs to be replaced. Before you do, I suggest one more test.

And this is to test to make sure that the PCM is not fried. This is a very simple test and it requires that you jumper the IAT sensor circuits A and B together (using a jumper wire) and then checking, with your scan tool in Live Data mode, that the intake air temperature (IAT) sensor's PID is now reading 300 °F.

For this test, go to: TEST 3: Jumpering the IAT Sensor Circuit.

TEST 3: Jumpering The IAT Sensor Circuit

In this test step, I'm gonna' show you how to eliminate the PCM (Powertrain Control Module = fuel injection computer) as bad.

Don't worry, this is a very simple test! What's involved is using a jumper wire to jumper the two IAT sensor wires together (see the illustration above). You'll need to use a very thin wire to jumper the connector's terminals together (to avoid damaging them).

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. 1

   With your scan tool connected to your vehicle, and the key in the ON position, scroll down to the IAT sensor PID and observe the current value displayed.

2. 2

   Disconnect the IAT sensor from its connector.
   
   Using a jumper wire, jumper two terminals of the IAT sensor connector together.
   
   IMPORTANT: Be careful that your jumper wire doesn't damage the two metal terminals.

3. 3

   Your scan tool should now read 300 °F for the intake air temperature (IAT) sensor reading.
   
   You'll also see DTC P0112.

Let's take a look at your test results:

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

You have now confirmed 3 very important things:

1. That the PCM is seeing an extreme cold temperature around -30 °F (TEST 1).
2. That there are no shorts in the sensor's wiring or in its connector (TEST 2).
3. That the PCM is OK (TEST 3).

Therefore, you can confidently conclude that the IAT sensor is bad and needs to be replaced.

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).

Although testing the wiring between the PCM and the IAT sensor is beyond the scope of this tutorial, you now have eliminated the IAT sensor as the source of the P0113.

More Test Tutorials

If this tutorial was helpful/informative, you can find a complete list of tutorials here: 3.8L GM Index Of Articles.

Here's a sample of the tutorials you'll find there:

• How Can I Tell If My Automatic Transmission Needs An Overhaul?
• How To Diagnose Misfire Codes P0300-P0306 (GM 3.8L).
• How To Do A Cylinder Balance Test (GM 3.8L V6).
• How To Test The 3.8L GM Crank Sensor With A Multimeter.
• GM 3.8L Ignition Coil Pack Tests (at: easyautodiagnostics.com).
• GM 3.8L Ignition Control Module and Crank (3X, 18X) Sensor Test (at: easyautodiagnostics.com).