TEST 3: Testing The Heater Element's Resistance
OK, having reached this point, we now know that the Bank 1 Sensor 1 oxygen (O2) sensor is getting power and Ground.
The next step (and the last one)... is to check to see if the oxygen sensor's heater element is fried inside the O2 sensor itself.
This is a pretty easy test that you can do with your multimeter in Ohms mode and with the O2 sensor still installed on the exhaust manifold or exhaust pipe.
OK, this is what you need to do:
- Disconnect the oxygen sensor from the engine wiring harness connector (if it isn't already from the previous tests).
- Locate the O2 sensor wires that correspond to:
- The circuit D.
- The circuit E.
- Both of these letters should be embossed on the O2 sensor's connector to aid you in further identifying the circuits you need to test.
- With your multimeter in Ohms mode, check the resistance of this circuit.
- NOTE: Remember, you're testing the oxygen sensor itself.
- If all is OK, you should see about 4.5 Ω (Ohms).
- If the heater element is fried, your multimeter will show an open (usually indicated by the letters OL).
Let's take a look at your test results:
CASE 1: Your multimeter showed the indicated resistance. This tells you that you that the heater element within the oxygen sensor is OK.
CASE 2: Your multimeter showed an open circuit (OL). This confirms that the heater element inside the O2 sensor is bad. Replace the Bank 1 Sensor 1 oxygen sensor with a new one.
Where To Buy The O2 Sensor And Save
There's a good chance that you can buy the original AC Delco upstream oxygen (O2) sensor online for a whole lot cheaper than somewhere local.
The following links will help you comparison shop for the AC/Delco and aftermarket upstream oxygen sensor:
More 3.5L GM Tutorials
If you enjoyed and/or found this ‘How to’ article helpful, I have written several more 3.5L specific test articles. You can find a complete list of 3.5L tutorials here: GM 3.5L Index Of Articles.
- How To Test For A Blown Head Gasket (GM 3.5L, 4.2L).
- How To Diagnose A P0141 Heater Performance Bank 1 Sensor 2.
- How To Test The Intake Air Temp (IAT) Sensor (GM 3.5L).
- Ignition Coil-On-Plug (COP) Test (GM 3.5L, 4.2L).
- How To Test The Mass Air Flow (MAF) Sensor (GM 3.5L).
- How To Bench Test A Starter Motor (Step By Step) (at: easyautodiagnostics.com).
If this info saved the day, buy me a beer!