Troubleshooting P0112: Intake Air Temperature Circuit Low Input
START HERE: At the core of your Honda's P0112 IAT Sensor Circuit Low Voltage OBD II diagnostic trouble code (DTC) is the fact that the PCM thinks that the temperature of the air, that the engine is breathing, is at 300°F (150°C) or more.
With this info in mind, testing the IAT sensor becomes really easy and I'll show you how to troubleshoot it in a step-by-step manner. You'll need a scan tool with Live Data capability to follow along my testing instruction (if you don't have a scan tool and you need to buy one, check out my Actron CP9580 Scan Tool Review).
There are 3 basic and very simple tests that I'm gonna' show you so that you can test the P0112 IAT Sensor Circuit Low Voltage diagnostic trouble code (DTC) lighting up your Honda's check engine light (CEL).
Basically, you will:
- Confirm the IAT sensor's temperature value.
- The first thing we need to do is to see what temperature the IAT sensor is reporting.
- What we're looking for is to see if the IAT sensor is reporting a temp that's 300°F (150°C) or higher.
- TEST 1: Checking The Intake Air Temperature Value.
- Check that the IAT sensor connector's wiring is not shorted together.
- This involves removing the hard plastic protector that's over the wires and inspecting the condition of the two IAT sensor wires.
- We'll also do a wiggle test of the IAT sensor's 2 wires.
- TEST 2: Checking The Condition Of The IAT Sensor's 2 Wires.
- Unplugging the IAT sensor and verifying the PCM sees an extreme cold temperature.
- In this test step, we'll unplug the IAT sensor from its connector and then, via the scan tool's Live Data mode, see if the PCM now reads -4 °F (-20 °C).
- This test will help you to eliminate a bad PCM and/or a hidden electrical short somewhere in the wiring between the PCM and IAT sensor.
- TEST 3: Disconnecting the IAT Sensor From Its Connector.
TEST 1: Checking The Intake Air Temperature Value
As mentioned before, when your Honda's PCM registers a trouble code P0112 IAT Sensor Circuit Low Voltage, it's seeing an air temperature of 300°F (150°C) or higher.
You and I know that this is impossible (we'd be all dead if the outside air temp was really that high!), so the first thing we need to do is confirm this via a scan tool with Live Data capability.
Yup, a scan tool with Live Data capability will let us see the temperature the IAT sensor is reporting either in degrees Fahrenheit or Celsius (depending on how you have it set up).
If you don't have a scan tool and you need to buy one, check out my Actron CP9580 Scan Tool Review.
IMPORTANT: To ensure the accuracy of this test, your Honda's engine should be completely cold before you start.
OK, this is what you need to do:
Connect your scan tool to your Honda (or Acura) car or mini-van and turn the key to the on position.
NOTE: This test is done with the Key On Engine OFF (KOEO).
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 what the acronym PID stands for, it's: Parameter 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:
- -4°F (-20°C).
- 300°F (-150°C).
- The current outside air temperaute.
Let's interpret your test results:
CASE 1: Your scan tool shows a 300 °F reading. This confirms that there is a problem with the intake air temperature (IAT) sensor.
This test result also confirms that the code P0112 IAT Sensor Circuit Low Voltage Input, that was stored in the PCM's memory is telling you the truth.
The most likely cause will be that the IAT sensor circuits (wires) are shorted together. This usually happens in the section of the 2 wires nearest to the IAT sensor's connector.
The next step is to physically check the condition of the wires and do a simple wiggle test. Go to: TEST 2: Checking The Condition Of The IAT Sensor's 2 Wires.
CASE 2: Your scan tool shows a -4 °F (-20°C) reading. This confirms that you do have a problem with the intake air temperature (IAT) sensor or its circuits.
Seeing an extreme cold temperature of -4 °F (-20°C) indicates one of two things, either that the IAT sensor is bad or the IAT sensor connector's wires have an open-circuit problem (think unplugged sensor). You'll also see a diagnostic trouble code P0113 (IAT Sensor Circuit High Voltage) stored in the PCM's memory.
For further testing of this condition, see the following tutorial: P0113 IAT Sensor Circuit High Voltage (Honda 2.2L, 2.3L).
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 and more importantly, that the problem is intermittent.
But, since your scan tool retrieved a DTC P0112 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 P0112 DTC does come back, repeat this test once more.