TEST 2: Checking For An Internal Open-Circuit/Short-Circuit Issue
In this test section, we'll check the MAT sensor for an internal open-circuit or short-circuit issue.
An open-circuit issue means there's a break in the electrical circuit inside the MAT sensor. A short-circuit issue means there's a direct connection between two parts of the circuit.
We'll use a multimeter in Ohms mode to check the MAT sensor for these issues. The resistance reading on the multimeter will show us if there's a problem.
If the MAT sensor has a short-circuit problem, your multimeter will display a low resistance value, typically near 0 Ohms. This indicates that the voltage supplied to the MAT sensor is flowing through a direct path, bypassing its thermistor.
If the MAT sensor has a open-circuit problem, your multimeter will display a high resistance value, close to infinity (OL or "over limit"). This indicates that there is a break in the voltage flow, preventing it from reaching the sensor's thermistor.
IMPORTANT: For the accuracy of your test, the engine must be completely cold before starting this test.
These are the test steps:
- 1
Turn off the ignition and disconnect the battery from its negative (-) cable.
- 2
Locate the MAT sensor and disconnect it from its connector.
- 3
Set the multimeter to Ohms mode.
- 4
Measure the resistance between the male spade terminals of the MAT sensor using the multimeter test leads.
- 5
Does the reading show an open-circuit or short-circuit problem?
Let's examine your test results:
CASE 1: The resistance value is neither 0 Ohms nor infinity (OL). So far so good since this test result tells you that the MAT sensor does not have an internal short-circuit or open-circuit problem.
Your next step is to go to: TEST 3: Checking Temperature To Resistance Value Relationship.
CASE 2: The resistance value is 0 or near 0 Ohms. This indicates an short-circuit issue with the MAT sensor and confirms its bad. Replace the MAT sensor.
CASE 3: The resistance value is infinity (OL or "over limit"). This indicates an open-circuit issue with the MAT sensor and confirms its bad. Replace the MAT sensor.
TEST 3: Checking Temperature To Resistance Value Relationship
In this last test section, we'll check the relationship between the resistance value of the MAT sensor and the air temperature around you.
As you already know, the resistance value of the MAT sensor changes with temperature. What you may not know is that the MAT sensor temperature measurement is usually within plus or minus 10 degrees of the ambient temperature around the engine.
So, for the accuracy of your MAT sensor test, it's important to start your test with a completely cold engine.
Once you've obtained the resistance value of the MAT sensor, you'll compare it to the Temperature To Resistance Chart in the image viewer above.
If the MAT sensor is functioning correctly, the temperature it reports should be within ± 10° F of the ambient temperature of your location.
Let's get going:
- 1
Take note of the ambient temperature around you.
- 2
Locate the MAT sensor and disconnect it from its connector.
- 3
Set the multimeter to Ohms mode.
- 4
Measure the resistance value of the MAT sensor across its male terminals.
- 5
Take note of the resistance value the multimeter displays.
- 6
Compare the measured resistance value to the Temperature To Resistance Chart.
The measured resistance value should fall within the specified range for the current temperature (± 10° F) around you.
Let's interpret your test results:
CASE 1: The resistance value IS NOT within the specified range for the current ambient temperature. This test result tells you the MAT sensor is bad and needs replacement.
CASE 2: The resistance value is within the specified range for the current ambient temperature. This tells you that the MAT sensor is functioning properly.
More 2.5L Chevy S10 Pickup, GMC S15 Pickup, And GMC Sonoma Tutorials
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Here's a sample of the tutorials you'll find in the index:
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