TEST 1: Checking The Intake Air Temperature Value
The fastest and easiest way to test the intake air temperature (IAT) sensor is using a scan tool with Live Data capability.
We're gonna' start out by connecting the scan tool and eye-balling what temperature the IAT sensor is outputting.
Now, it's possible to check the IAT sensor without a scan tool. How? By measuring the resistance of the IAT sensor and then comparing them to the actual ambient temperature that your pickup or SUV 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.
OK, this is what you need to do:
- Connect your scan tool to your pickup or car.
- Once the scan tool has powered up, go to its Live Data mode.
- Scroll down to the PID labeled IAT (°F)
- In case you're wondering, PID stands for: Parameter ID (ID = Identification).
- The scan tool should register a temperature that should be within ±10 °F of ambient temperature (if all is normal)
- So let's say that it's 50 °F outside, then the IAT sensor PID should register something between 40 to 60 °F.
- 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:
- - 30 to -40 °F (that's negative 30 to 40 °F).
- 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’ somewhere inside the MAF sensor (remember the IAT sensor is part of the MAF sensor assembly).
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.
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.
This temperature reading also confirms that the diagnostic trouble code P0112 (IAT Sensor Circuit Low Voltage) stored in the PCM's memory is correct.
The next step is to see if the IAT sensor wires are not shorted together, go to: TEST 3.
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 P0112 or 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 it does, then repeat this test once more.
TEST 2: IAT Sensor Circuit High Voltage
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 MAF sensor connector (remember, the IAT sensor is part of the MAF sensor), while you observe your scan tool to see if this has an effect on your IAT sensor temperature reading.
Why a wiggle test? Well, because the two most likely causes (of this P0113 Code and the temperature reading) will be:
- A bad MAF sensor connector.
- Or a bad intake air temperature (IAT) sensor.
And so, if the MAF sensor connector is bad or making a false contact, then wiggling the connector should have an effect on the IAT sensor's reading displayed live on your scan tool in Live Data mode.
OK, this is what you need to do:
- Connect your scan tool and get to its Live Data mode.
- Scroll down to the PID for the IAT sensor.
- -30 to -40 °F temperature reading should still be present.
- Now, have a helper (or yourself) gently wiggle the MAF sensor connector as you keep your eyeballs on the IAT sensor PID on your scan tool.
- If the MAF sensor connector is bad, you'll see the IAT sensor reading go from -30 to -40 °F to a normal temperature.
- 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 MAF connector caused the temperature to change. This test result tells you that the connector is bad and needs to be replaced.
Gently wiggling the MAF sensor connector should have no effect on the IAT sensor reading displayed on the scan tool, unless the connector is bad. Since wiggling the connector did have an effect, you now know that replacing the MAF sensor connector will solve the IAT sensor and P0113 Code problem.
CASE 2: Wiggling the MAF connector DID NOT cause the temperature to change. This tells you that the MAF sensor connector is OK.
Since your scan tool is still reading a -30 to -40 °F IAT sensor reading, the next step is jumper the IAT sensor circuits A and B together (using a jumper wire) to make the PCM believe that the intake air temperature (IAT) sensor is sending it a 300 °F reading.
For this test, go to: TEST 5.
