TEST 3: O2 Heater Resistance Test

P0141, P0161 Downstream O2 Sensor Test (1999-2002 GM 4.8L, 5.3L, 6.0L)

In this test section, we're gonna' check the heater element itself (which is inside the O2 sensor).

So far in your testing, you've checked and confirmed:

  1. The downstream O2 sensor you're testing does have 10 to 12 Volts being fed to it (TEST 1).
  2. That it also has a good path to Ground (TEST 2).

Depending on what's easier for you, you can check this with the O2 sensor on or off the vehicle.

OK, this is what you need to do:

  1. Disconnect the downstream oxygen sensor from the engine wiring harness connector (if it isn't already from the previous tests).
    1. NOTE: The O2 sensor must be disconnected from the vehicle's connector for this test!
  2. Locate the O2 sensor wires that correspond to:
    1. The circuit C and D.
    2. 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.
  3. With your multimeter in Ohms mode, probe the terminals that correspond to the letters C and D of the O2 sensor connector.
    1. NOTE: Remember, you're testing the oxygen sensor itself.
    2. If all is OK, you should see about 5 to 16 Ω (Ohms).
    3. 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 the heater element within the oxygen sensor is OK.

CASE 2: Your multimeter showed an open circuit (OL). Replace the downstream oxygen sensor your currently testing, since this result confirms it is bad.

Depending on what downstream oxygen sensor you're testing (either Bank 1 Sensor 2 or Bank 2 Sensor 2), replacing the oxygen sensor will solve the P0141 or P0161 diagnostic trouble code.

Here's why: You know, from your testing, that the O2 sensor's heater element is getting both power and Ground (in TEST 1 and TEST 2 respectively). In this test section, you have confirmed that the heater element is fried (since it shows an OL on your multimeter), therefore you can conclude with confidence that the O2 sensor is bad.

Where To Buy The Oxygen Sensor And Save Some $$$

You could buy the downstream oxygen sensor at your local auto parts store but you'll end up paying quite a bit for it (I'm sure you've already called and priced the O2 sensor) or you could buy it online and save a few bucks.

Don't worry if the image (of the O2 sensor) doesn't match exactly what's on your vehicle. Why? Because when you click on the O2 sensor below (to find out more about it), you'll be asked if you want to double-check if that is the O2 sensor that fits your specific vehicle.

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Cadillac Vehicles:
  • Escalade 5.3L, 6.0L
    • 2002
Chevrolet Vehicles:
  • Avalanche 5.3L
    • 2002
  • Silverado 1500, 2500, 3500 4.8L, 5.3L
    • 1999, 2000, 2001, 2002
  • Suburban 1500, 2500 5.3L
    • 2000, 2001, 2002
Chevrolet Vehicles:
  • Tahoe 4.8L, 5.3L
    • 2000, 2001, 2002
GMC Vehicles:
  • Sierra 1500, 2500, 3500 4.8L, 5.3L, 6.0L
    • 1999, 2000, 2001, 2002
  • Yukon Denali 1500, 2500 4.8L, 5.3L, 6.0L
    • 2000, 2001, 2002