TEST 2: Checking The Condition Of The IAT Sensor's 2 Wires
After confirming that your Honda's PCM is indeed sensing a -4°F (-20°C) intake air temperature with your scan tool, the next step is to check to see if the IAT sensor's connector is causing a false contact or if the sensor's wires are broken.
Remember, what causes the PCM to register a P0113 IAT Sensor Circuit High Voltage Input is that it thinks that the IAT sensor has somehow become unplugged, either due to an internal failure or a problem in the wire between it and the sensor.
So in this test step we'll check for a problem with the IAT sensor's connector and in the wiring.
NOTE: We don't have to check the entire length of the wiring between the PCM and IAT sensor connector, just the length nearest to the IAT sensor's connector (about 6 inches away from IAT sensor's connector).
OK, this is what you need to do:
- 1
Remove the hard plastic protector that's over the wires.
You need to expose the IAT sensor's wires starting from the connector to about 6 inches away (from the connector). - 2
Check for dry-rot and/or insulation peeling off the 2 IAT sensor wires.
The most likely place you'll find this condition (dry-rot and/or insulation peeling off) is right near the IAT sensor's connector. - 3
Check the condition of the IAT sensor's connector.
What you're looking for is to make sure that it's not broken or that the metal terminals (inside the connector) are free of any damage that could cause a false contact condition. - 4
Have a helper wiggle the 2 IAT sensor wires while you observe the IAT sensor's PID (on your scan tool).
What you're looking for is to see if wiggling the wires has any effect on the temperature reported on your scan tool.
Let's interpret your test results:
CASE 1: The wires have dry-rot and/or insulation peeling off. This condition is the most likely cause of code P0113. You need to repair or replace these wires.
After repairing the wires, road test the vehicle and see if the P0113 code comes back or not.
CASE 2: The IAT sensor's connector is broken or has a problem. This condition is the most likely cause of code P0113. You need to repair or replace these wires.
After repairing the wires, road test the vehicle and see if the P0113 code comes back or not.
CASE 3: Wiggling the 2 IAT sensor wires caused a change in the temperature reading. This test result tells you that the wires do have a problem.
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 4: You found no problems such as: The wires DO NOT HAVE dry-rot and ARE NOT shorted together and 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 disconnect the IAT sensor from its connector and then jumper the connector's terminals with a jumper wire. This will cause the PCM to read a temperature of 300°F (150°C), which you can see with your scan tool in Live Data mode.
For this test, go to: TEST 3: Jumpering Together the IAT Sensor's Circuits.
TEST 3: Jumpering Together The IAT Sensor's Circuits
I've seen cases where the PCM failed and falsely accused the IAT sensor as having failed when it really hadn't.
A Honda PCM going bad doesn't happen every day but its still a possibility we need to eliminate.
Also, we need to eliminate the possibility that there's a hidden electrical open-circuit problem somewhere in the IAT sensor's wiring, between the PCM and IAT sensor.
Thankfully there's a very simple way to test both of these possibilities and it's done by checking the PCM's response to jumpering together the IAT sensor's 2 wires. If the PCM now records an extreme hot temperature of 300°F (150°C), you now know that both the wiring and the PCM are OK.
OK, here's what you'll need to do:
- 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
Disconnect the IAT sensor from its connector and jumper its two metal terminals together with a jumper wire.
IMPORTANT: Take extreme care to not damage the connector's terminals with the jumper wire or you'll end up damaging the terminals. - 3
Your scan tool should now read 300°F (150°C) for the intake air temperature (IAT) sensor reading.
- The PCM may set DTC P0112 IAT Sensor Circuit Low Voltage.
Let's take a look at your test results now:
CASE 1: The scan tool registered 300°F (150°C). 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:
- That the PCM is seeing an extreme hot temperature around 300 °F (TEST 1).
- That there are no shorts in the sensor's wiring or in its connector (TEST 2).
- 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 (150°C). 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 and the PCM itself are beyond the scope of this tutorial, you now have eliminated the IAT sensor as the source of the P0113.
