Oxygen Sensor Heater Test -P0135 (2000 4.7L Dodge Dakota, Durango)

TEST 2: Verifying The Heater Element Is Getting Ground

Now that you have confirmed that the upstream O2 sensor's heater is being fed power by the ORG/DK GRN wire, the next step is verifying the heater element is getting Ground.

The front oxygen sensor's heater element is fed Ground by the black (BLK) wire (of the engine wiring harness upstream O2 sensor's electrical connector).

To see if Ground is indeed present (or not) we'll do another simple multimeter voltage test.

NOTE: The illustration of the connector above is of the connector on the oxygen sensor itself. To check for Ground, you need to test the BLK wire of the engine wiring harness sensor connector.

These are the test steps:

1. 1

   Locate the BLK wire of the O2 sensor's engine wiring harness connector.
   
   NOTE: Remember, you'll test the wire that's on the engine wiring harness connector side and NOT on the O2 sensor itself.

2. 2

   Place your multimeter in Volts DC mode and connect the red multimeter test lead to battery (+).
   
   With the black multimeter test lead, probe the BLK wire of the O2 sensor's harness connector.

3. 3

   With the Key On, engine Off, this wire should have 10 to 12 Volts DC.

Let's take a look at your test results:

CASE 1: The multimeter registered 10 to 12 Volts DC. This tells you that the upstream oxygen sensor's heater element is getting Ground.

So far you've confirmed that the HO2S 11's heater element is getting both power and Ground. The next step is to check the heater element's resistance with your multimeter. For this test, go to: TEST 3: Testing The Heater Element's Resistance.

CASE 2: The multimeter DID NOT register 10 to 12 Volts DC. Re-check all of your connections and make sure you're testing the correct terminal.

If you still don't see 10 to 12 Volts DC, then the most likely cause of this missing Ground is an 'open' in the BLK wire between the O2 sensor's engine wiring harness connector and chassis Ground.

TEST 3: Testing The Heater Element's Resistance

Having check the basics (power and Ground to the upstream oxygen sensor's heater), in this last test, we're gonna' check the O2 sensor's heater element's resistance.

If the upstream O2 sensor's heater element's resistance is not within specification, then we can conclude that the upstream sensor is fried and the cause of the P0135: P0135: HO2S 11 Circuit Malfunction trouble code lighting up the check engine light.

NOTE: Just a reminder that the upstream 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:

1. 1

   Locate the O2 sensor terminals number 1 and number 2 of the O2 sensor connector itself (not the engine wiring harness O2 connector).

2. 2

   With your multimeter in Ohms mode, probe terminals number 1 and number 2 of the O2 sensor itself.

3. 3

   If all is OK, you should see about 3 to 30 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 O2 heater's resistance is within factory specification. This test result tells you that the HO2S 11's heater is OK.

CASE 2: Your multimeter showed an open circuit (OL). This confirms that the HO2S 11's heater element is fried. Replacing the HO2S 11 with a new one will solve the P0135 trouble code lighting up the check engine light (CEL).

Taking into account that you have:

• Confirmed that the upstream O2 sensor's heater element is getting power (TEST 1).
•      -AND-
• Confirmed that the upstream O2 sensor's heater element is getting Ground (TEST 2).
•      -AND-
• In this test, you have confirmed that the heater element's resistance is out of specification.

... You can correctly conclude that your 4.7L Durango's (or Dakota's) upstream O2 sensor needs to be replaced with a new one.

Location Of The Oxygen Sensors

NOTE: The above illustration is for the 2000 4.7L Federal emissions equipped Dodge Durango / Dakota. These vehicles come equipped with 2 oxygen sensors instead of 4.

More 4.7L Dodge Diagnostic Tutorials

You can find a complete list of 4.7L Dodge tutorials in these two indexes:

• Dodge 4.7L Index Of Articles.

Here's a small sample of the tutorials you'll find in the index:

• How To Test The MAP Sensor (2000-2001 4.7L Dakota, Durango).
• How To Test The Throttle Position Sensor (2000-2007 4.7L Dodge).
• How To Test The Fuel Injectors (Dodge, Jeep 4.7L V8) (at troubleshootmyvehicle.com).
• How To Test For A Blown Head Gasket (4.7L Chrysler, Dodge, Jeep) (at troubleshootmyvehicle.com).
• How To Test The COP Ignition Coils (Chrysler, Dodge, Jeep 4.7L) (at troubleshootmyvehicle.com).