Testing (DTC) P0135: HO2S 11 Circuit Malfunction can be done without any expensive diagnostic test equipment... all you'll need is a multimeter.
A trouble code P0135 signals a problem with the internal heater of the upstream oxygen sensor.
In this tutorial, I'll show you the 3 basic tests you'll need to perform to diagnose the front oxygen sensor.
NOTE: This tutorial only applies to the 2000 4.7L V8 Dodge Dakota/Durango with non-California (Federal) emissions. The federal emissions Dakota/Durango only use 2 oxygen sensors where as the California emissions uses 4 O2 sensors.
NOTE: This oxygen sensor is known by several different names:
- Front Heated Oxygen (O2) Sensor.
- HO2S 11.
- Upstream Oxygen (O2) Sensor.
- Oxygen Sensor Bank 1 Sensor 1.
Here are the contents of this tutorial:
- Circuit Descriptions of the Upstream Oxygen Sensor.
- TEST 1: Verifying the Heater Element is Getting Power.
- TEST 2: Verifying the Heater Element is Getting Ground.
- TEST 3: Testing the Heater Element's Resistance.
- Location Of The Oxygen Sensors.
- Where to Buy the Oxygen Sensor and Save Some $$$.
- More 4.7L Dodge Diagnostic Tutorials.
If you need to troubleshoot the rear front O2 sensor (HO2S 1/2), take a look at the following tutorial:
Puedes encontrar este tutorial en Español aquí: Calentador del Sensor de Oxígeno -P0135 (2000 4.7L Dakota, Durango) (en: autotecnico-online.com).
Circuit Descriptions of
the Upstream Oxygen Sensor
The front heated oxygen sensor (HO2S 11), on your 4.7L V8 equipped Dodge Dakota (or Durango) is a 4 wire oxygen sensor that has an internal heater.
2 wires are for actual oxygen sensing part of the sensor assembly. The other 2 are to supply the heater with power and ground.
NOTE: You can find the location of the front oxygen sensor (HO2S 11) here: Location Of The Oxygen Sensors.
Below, you'll find the color of the wires of the engine wiring harness oxygen sensor connector for sensor HO2S 11:
|Upstream Oxygen Sensor (HO2S 11) Pinout
(2000 4.7L Dakota -Durango w/ Federal Emissions)
|1||ORG/DK GRN (or DK GRN/RED)||Heater Power (+)|
|2||BLK||Heater Ground (-)|
|3||BLK/LT BLU||O2 Signal Ground|
|4||LT GRN/RED||O2 Signal|
TEST 1: Verifying the Heater Element is Getting Power
The first order of business is to check that the front oxygen sensor (HO2S 11) is getting power.
Of the 4 wires sticking out of the engine wiring harness O2 sensor connector... it's the orange with dark green (ORG/DK GRN) wire that feeds power to the HO2S 11 heater element.
CAUTION: The O2 sensor can get and stay very hot! Perform this test with a completely cold engine. Be careful and take all necessary safety precautions! Also, if you raise your vehicle with a jack, place it on jack stands.
IMPORTANT: The illustration of the connector above is of the connector on the oxygen sensor itself. To check for power, you need to test the ORG/DK GRN wire of the engine wiring harness sensor connector.
OK, this is what you'll need to do:
Locate the front oxygen sensor and disconnect it from its engine wiring harness connector.
Locate the ORG/DK GRN wire of the engine wiring harness oxygen sensor connector.
With your multimeter in Volts DC mode, probe the ORG/DK GRN wire with the red multimeter lead.
Ground the black multimeter lead directly on the battery's negative terminal.
With the Key On Engine Off (KOEO), the ORG/DK GRN wire should have 10 to 12 Volts DC.
Let's take a look at your test results:
CASE 1: Your multimeter confirms that the ORG/DK GRN wire has 10 to 12 Volts DC- This confirms that the front oxygen sensor's heater element is getting power.
The next step is to make check that the BLK wire, of HO2S 11 engine wiring harness connector, is feeding ground to the heater element. For this test, go to TEST 2: Verifying the Heater Element is Getting Ground.
CASE 2: Your multimeter confirms that the ORG/DK GRN wire DOES NOT have 10 to 12 Volts DC- Re-check that you're testing the correct wire and that the Key is in the RUN position (but don't crank or start the engine) and re-test.
If your multimeter still does not register 10 to 12 Volts DC... then you can conclude that HO2S 11 itself IS NOT BAD... since without power, the heater element won't work.
Although it's beyond the scope of this article... the next step is to find out why this battery power is missing using a wiring diagram.