TEST 2: Testing The Heater Element's Resistance
In this test section, we're gonna' make sure that the heater element's resistance is within specification (11 to 16 Ohms) with the multimeter in Ohms mode.
If the rear O2 heater's internal resistance IS NOT within spec and in TEST 1 you've confirmed that it's getting power and Ground, then you can confidently conclude that the O2 sensor is bad and needs to be replaced. Also, this tells you that replacing the rear O2 sensor will solve the P0141 DTC that's lighting up your Corolla's check engine light (CEL).
NOTE: Just a reminder that the oxygen sensor has to be completely cold before proceeding with this test since the manual calls for the O2 sensor to be at room temperature for the resistance test.
OK, this is what you need to do:
Locate the O2 sensor terminals number 1 and number 2 of the O2 sensor connector itself (not the engine wiring harness O2 connector).
With your multimeter in Ohms mode, probe terminals number 1 and number 2 of the O2 sensor itself.
If all is OK, you should see about 11 to 16 Ωs on your multimeter.
If the heater element is fried, your multimeter will show an open (usually indicated by the letters OL) or a number over 10 K Ωs.
Let's take a look at your test results:
CASE 1: The multimeter confirms that the rear O2 heater's resistance is within factory specification. This test result tells you that the rear O2's heater is OK.
CASE 2: Your multimeter showed an open circuit (OL). This confirms that the rear O2's heater element, on your Corolla, is fried. Replacing the rear oxygen sensor with a new one will solve the P0141 trouble code lighting up the check engine light (CEL).
You can correctly conclude that your 1.6L Toyota Corolla downstream O2 sensor needs to be replaced if you have:
- Confirmed that power and Ground is reaching the sensor's heater (TEST 1).
- In this test you have confirmed that the heater element's resistance is out of specification.
More 1.6L Toyota Diagnostic Tutorials
You can find a complete list of 1.6L Toyota tutorials in these two indexes:
Here's a small sample of the tutorials you'll find in the index:
- How To Do A Cylinder Balance Test (1.6L Toyota Corolla).
- How To Test The Throttle Position Sensor (1.6L Toyota Corolla).
- TPS Idle Switch Multimeter Test (1.6L Toyota Corolla).
- How To Test Engine Compression (1.6L Toyota Corolla).
- How To Test The Fuel Injectors (1.6L Toyota Corolla).
If this info saved the day, buy me a beer!