TEST 8: 5 Volt Reference Circuit
In this section, we're gonna' check the intake air temperature (IAT) sensor's 2 circuits in one test.
These two circuits are the Ground circuit (wire letter A) and the 5 Volt Reference circuit (wire letter B).
What we'll do is unplug the MAF sensor and then probe these 2 wires (of the MAF sensor connector itself) with your multimeter in Volts DC mode.
NOTE: That's right, the test has to be done with the MAF sensor disconnected and as such, here are some important precautions to keep in mind:
- Don't probe the front of the MAF sensor connector with the multimeter test leads. This can damage them and then you're gonna' be in a heap of trouble later when the connector causes a false contact.
- You can back probe the connector with special back probes.
- Or, do what I do: use wire piercing probes.
OK, safety lesson over, this what you'll need to do to get this test done:
- Place the multimeter in Volts DC mode.
- Disconnect the mass air flow (MAF) sensor from its connector.
- Locate the wires identified with the letter A and letter B.
- Wire A is the Black wire.
- Wire B is the Tan wire.
- Connect the red multimeter test lead to this letter B wire using an appropriate tool (like a Wire Piercing Probe).
- Connect the black multimeter test lead to the letter A wire.
- Turn the key to the ON position (RUN position)
- Your multimeter should register 4.5 to 5 Volts DC.
- When done, turn the key Off and interpret your results below:
CASE 1: The multimeter recorded 4.5 to 5 Volts DC- So far so good, since this test result tells you that two very important things:
- That the PCM is supplying a Ground on wire A.
- That the PCM is supplying 5 Volts on wire B.
NOTE: If you're coming from TEST 7 or TEST 8, then this result tells you that the most likely cause of the DTC P0113 (Intake Air Temperature (IAT) Sensor Circuit High Voltage) or DTC P0112 (Intake Air Temperature (IAT) Sensor Circuit Low Voltage) is an intermittent short. Intermittent problems are the hardest to find and resolve. I suggest erasing the DTC and road testing the vehicle to see if the DTC P0112 or P0113 comes back and repeating the tests.
CASE 2: The Multimeter DID NOT record 4.5 to 5 Volts DC. Make sure that you're testing the correct wires, that your connections are OK, and repeat the test.
Then there's one of two things wrong:
- That the PCM (Fuel Injection Computer) IS NOT supplying 5 Volts on wire D.
- That the PCM (Fuel Injection Computer) IS NOT supplying a Ground on wire E.
NOTE: This test result exonerates the IAT sensor as bad, since without power (5 Volts) or Ground, the IAT sensor won't work.
You'll need to troubleshoot the missing 5 Volt Reference signal or the Ground to resolve the IAT sensor problem and diagnostic trouble code (DTC).
Intake Air Temp (IAT) Temperature/Resistance Chart
Below you'll find the temperature to resistance relationship of the intake air temperature (IAT) sensor.
| Temperature / Resistance | ||
|---|---|---|
| °F | °C | Ohms (Ω) |
| 302 °F | 150 °C | 47 Ω |
| 284 °F | 140°C | 60 Ω |
| 266 °F | 130 °C | 77 Ω |
| 248 °F | 120 °C | 100 Ω |
| 230 °F | 110 °C | 132 Ω |
| 212 °F | 100 °C | 177 Ω |
| 194 °F | 90 °C | 241 Ω |
| 176 °F | 80 °C | 332 Ω |
| 158 °F | 70 °C | 467 Ω |
| 140 °F | 60 °C | 667 Ω |
| 122 °F | 50 °C | 973 Ω |
| 113 °F | 45 °C | 1,118 Ω |
| 104 °F | 40 °C | 1,459 Ω |
| 95 °F | 35 °C | 1,802 Ω |
| 86 °F | 30 °C | 2,238 Ω |
| 77 °F | 25 °C | 2,796 Ω |
| 68 °F | 20 °C | 3,520 Ω |
| 59 °F | 15 °C | 4,450 Ω |
| 50 °F | 10 °C | 5,670 Ω |
| 41 °F | 5 °C | 7,280 Ω |
| 32 °F | 0 °C | 9,420 Ω |
| 23 °F | -5 °C | 12,300 Ω |
| 14 °F | -10 °C | 16,180 Ω |
| 5 °F | -15 °C | 21,450 Ω |
| -4 °F | -20 °C | 28,680 Ω |
| -22 °F | -30 °C | 52,700 Ω |
| -40 °F | -40 °C | 100,700 Ω |
IAT Sensor Test Summary
Testing the intake air temperature (IAT) sensor isn't hard to do. Hopefully this article was able to help you to troubleshoot the IAT sensor and/or diagnostic trouble codes P0112 or P0113.
If you'd like to add your two cents to this article and share your own diagnostic and repair experience with the rest of us, you can use the contact form below.
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To see all of the GM 4.8L, 5.3L, 6.0L specific articles here at troubleshootmyvehicle.com, go to: GM 4.8L, 5.3L, 6.0L Index Of Articles.
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