TEST 1: Checking The Intake Air Temperature Value
The very first thing that you and I need to do, before anything else, is to hook up a scan tool to your vehicle's diagnostic connector and check what the intake air temperature (IAT) sensor is reporting to the PCM (Powertrain Control Module = Fuel Injection Computer).
This of course requires a scan tool that can read Live Data. This scan tool can be a generic scan tool since you don't need the GM factory scan tool or an expensive professional technician level scan tool.
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 tells you that you definitely have a problem with the intake air temperature (IAT) sensor or its circuits.
This temperature reading also confirms that the diagnostic trouble code P0113 (IAT Sensor Circuit High Voltage) that you retrieved from the PCM's memory is right on the money.
The most likely cause will be that the circuit is ‘open’ somewhere inside the MAF sensor (remember the IAT sensor is part of the MAF sensor assembly).
To be a bit more specific, by ‘open’ I mean that somewhere in the two wires or the IAT Sensor, there's a break in the wire or that the IAT sensor is fried.
We'll find out in the next couple of tests. Go to: TEST 2: IAT Sensor Circuit High Voltage.
CASE 2: Your scan tool shows a 300+ °F reading. This tells you that you definitely 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) that you retrieved from the PCM's memory is right on the money.
To further your diagnostic of the IAT Sensor, go to: TEST 3: IAT Sensor Circuit Low Voltage.
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 you still have a DTC P0112 or P0113 registered on your PCM's memory, I recommend clearing the Diagnostic Trouble Code (DTC) and road testing your vehicle to see if the code comes back.
If it does, repeat this test once more.
TEST 2: IAT Sensor Circuit High Voltage
You've reached this test step 'cause a Diagnostic Trouble Code P0113 (IAT Sensor Circuit High Voltage) registered on your scan tool.
Also in TEST 1, you confirmed that the scan tool is reading an intake air temperature (IAT) of -30 to -40 °F.
In this test step, we're gonna' further troubleshoot this problem. The two most likely causes (of this code and the temperature reading) will be:
- A bad MAF sensor connector.
- Or a bad intake air temperature (IAT) sensor.
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 tells you that 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. So if it does, you have found the 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 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: Jumpering The IAT Sensor Circuits.
