TEST 2: Checking For An Internal Open-Circuit/Short-Circuit Issue
Now that you've confirmed the presence of an ECT sensor diagnostic trouble code stored in the ECM's memory, we'll perform a multimeter test in Ohms mode to check if there is an internal electrical issue with the ECT sensor.
Specifically, we need to see if the ECT sensor has suffered an internal open-circuit or short-circuit problem.
If the ECT sensor has an open-circuit problem, the multimeter will report a value of "OL" (or an infinite resistance value), indicating that the voltage supplied to the ECT sensor is not flowing through its thermistor.
On the other hand, if the ECT sensor has a short-circuit problem, the multimeter will report a value of "0 Ohms," indicating that the voltage supplied to the ECT sensor is flowing through a direct path, bypassing its thermistor.
IMPORTANT: For the accuracy of your test, the engine must be completely cold before starting this test.
Let's begin the test:
- 1
Turn off the ignition and disconnect the battery from its negative (-) cable.
- 2
Locate the ECT 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 ECT 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 ECT 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 ECT sensor and confirms its bad. Replace the ECT sensor.
CASE 3: The resistance value is infinity (OL or "over limit"). This indicates an open-circuit issue with the ECT sensor and confirms its bad. Replace the ECT sensor.
TEST 3: Checking Temperature To Resistance Value Relationship
This final test section focuses on checking the resistance to temperature relationship of the ECT sensor.
As mentioned earlier, as temperature changes, the resistance of the ECT sensor also changes. Each resistance value of the sensor corresponds to a specific temperature value (see chart above).
A good ECT sensor will report a temperature within plus or minus 10 degrees of the ambient temperature of your location.
IMPORTANT: The accuracy of this resistance to temperature test requires the engine to be completely cold. If the engine has been running, allow it to cool down completely before proceeding with the test.
OK, let's find out if the ECT sensor is reporting accurate temperature values:
- 1
Take note of the ambient temperature around you.
- 2
Locate the ECT sensor and disconnect it from its connector.
- 3
Set the multimeter to Ohms mode.
- 4
Measure the resistance value of the ECT 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 ECT 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 ECT sensor is functioning properly.
More 2.8L Chevy S10 Pickup, GMC S15 Pickup, And GMC Sonoma Tutorials
You can find a complete list of tutorials for the 2.8L V6 Chevrolet S10 pickup, GMC S15 pickup, and GMC Sonoma in this index:
Here's a sample of the articles, you'll find in the Index of Articles:
- How To Test The Fuel Pump (1988-1993 2.8L Chevrolet S10 Pickup, GMC S15 Pickup, GMC Sonoma).
- How To Test Engine Compression (1988-1993 2.8L Chevrolet S10 Pickup, GMC S15 Pickup, GMC Sonoma).
- How To Test The EGR Valve (1988-1993 2.8L Chevrolet S10 Pickup, GMC S15 Pickup, GMC Sonoma).
- How To Test The Starter Motor (1988-1993 2.8L V6 Chevrolet S10 Pickup, GMC S15 Pickup).
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