When the O2 sensor's heater element, on your 1993, 1994, or 1995 2.5L Dodge Dakota fails, the OBD I fuel injection computer will usually set a trouble code 21 (O2 Stays At Center) and light up the check engine light on your Dakota's instrument cluster.
In this tutorial, I'm gonna' explain how to make sure the O2 sensor is getting both power and Ground and how to test the resistance of the heater element (within the O2 sensor).
These three tests are easy and only require a multimeter. I've also included some links that'll save some money on the purchase of the O2 sensor.
Contents of this tutorial:
You can find this tutorial in Spanish here: Cómo Probar El Calentador Del Sensor De O2 (1993-1995 2.5L Dodge Dakota) (at: autotecnico-online.com).
Circuit Descriptions Of The Oxygen Sensor
Since your 2.5L Dodge Dakota's oxygen sensor has an internal heater, you'll notice that it has 4 wires sticking out of it.
The two wires that we'll be concerned about (in this tutorial) are the two that feed the heater element with power and Ground. The other two are the wires that connect to the oxygen sensing element inside the oxygen sensor.
Below you can find a brief description of the four wires of the O2 sensor.
TIP: The oxygen sensor's engine wiring harness connector has female terminals. The connector on the oxygen sensor itself has male spade terminals.
| O2 Sensor Pinout | ||
|---|---|---|
| Pin | Wire Color | Description |
| 1 | BLK/LT BLU | HO2S Low Signal |
| 2 | BLK/DK GRN | HO2S High Signal |
| 3 | BLK/TAN | Heater Element Ground |
| 4 | DK GRN/ORG | Heater Element 12 Volts (from Auto Shutdown Relay) |
TEST 1: Verifying Power And Ground
To get your OBD I trouble code 21 diagnostic under way, we need to confirm that the O2 sensor's heater element is getting power (12 Volts) and Ground.
The dark green with orange stripe (DK GRN/ORG) is the one that feeds power. The black with tan stripe (BLK/TAN) wire is the one that feeds Ground.
If your test results confirm that power and Ground are being fed to the heater element, then we can move on to the next test section (and test the heater elements resistance).
CAUTION: Perform all O2 sensor tests with a completely cold engine. If your Dodge Dakota's engine has been running for any amount of time, let it cool down completely. If you have to raise your pickup, to access the O2 sensor, use jack stands.
IMPORTANT: The power and Ground tests are done on the engine wiring harness sensor connector. This connector has round female terminals.
OK, this is what you'll need to do:
- 1
Locate the oxygen sensor and disconnect it from its engine wiring harness connector.
- 2
Set your multimeter to Volts DC mode and turn the key ON but don't crank or start the engine (this will power up the O2 sensor's engine wiring harness connector).
- 3
Make sure that the DK GRN/ORG wire is feeding battery power.
Connect the red multimeter test lead to the DK GRN/ORG wire and connect the black multimeter test lead to the battery Ground (-) terminal.
Your multimeter should read 10 to 12 Volts DC. - 4
Make sure that the BLK/TAN wire is feeding Ground.
Connect the black multimeter test lead to the BLK/TAN wire and connect the red multimeter test lead to the battery positive (+) terminal.
Your multimeter should read 10 to 12 Volts DC.
Let's take a look at your test results:
CASE 1: Your multimeter registered 10 to 12 Volts DC. This is the correct and expected test result.
Now that you have verified the basics, the next step is to make sure that he O2 sensor heater element resistance is within specification. For this test go to: TEST 2: Testing The Heater Element's Resistance.
CASE 2: The O2 sensor's heater is not getting power. This test result is usually the result of an 'open-circuit' in the DK GRN/ORG wire.
Although it's beyond the scope of this tutorial to check the wiring, your next step is to do a continuity test on the power wire between the O2's connector and the ASD relay connector.
CASE 3: The O2 sensor's heater is not getting Ground. The most likely cause of this is an open in the Ground wire between the O2 sensor connector and chassis Ground.
Although it's beyond the scope of this tutorial to check the wiring, your next step is to do a continuity test on the Ground wire between the O2's connector and chassis Ground.