The front oxygen sensor on the 1996-1997 2.4L Nissan Pickup is a 3-wire heated oxygen sensor. Sooner or later, the heater is gonna' burn out and the check engine light will light with a P0135 diagnostic trouble code (DTC) stored in the PCM's memory.
If this is what's brought you to this page, let me tell you right off the bat that testing the front O2 sensor's heater is a piece of cake. In this tutorial I'll show you how to do it using only a multimeter (no scan tool required).
Contents of this tutorial:
NOTE: If you need to test the rear 4-wire oxygen sensor's heater (trouble code P0141), see the following tutorial: Rear Oxygen Sensor Heater Test -P0141 (1996-1997 2.4L Pick Up).
Circuit Descriptions Of The Upstream Oxygen Sensor
Testing the front O2 sensor's heater involves 3 basic things. The first 2 tests are to make sure the front oxygen sensor's heater is getting power and ground. The last test involves checking its resistance with a multimeter.
Since the O2 sensor has 3 wires coming out of it, the first two tests (checking for power and ground) are done on the engine wiring harness connector.
The last test (checking the heater's resistance) is done on the oxygen sensor's connector.
TIP: The front oxygen sensor's engine wiring harness connector has female terminals. The connector on the oxygen sensor itself has male spade terminals.
Here's a brief description of the 3 wires of the front oxygen sensor:
|Upstream Oxygen Sensor Pinout
(1996-1997 2.4L Nissan Pickup)
|1||WHT||Heater Ground (-)|
|3||WHT||Heater Power (+)|
TEST 1: Verifying Power and Ground
The very first thing we'll do is to make sure that the front oxygen sensor's heater is getting power (12 Volts) and ground.
If your test results confirm that power and ground are present, then the next step is to check the heater element's internal resistance in TEST 2.
CAUTION: The oxygen sensor gets and stays very hot even after the engine is off! Perform this test with a completely cold engine. Be careful and take all necessary safety precautions! If you raise your vehicle with a jack, place it on jack stands!
IMPORTANT: The pinout in the illustration above is of the connector on the oxygen sensor itself. To check for power and ground, you'll test the outer 2 wires of the engine wiring harness sensor connector.
OK, this is what you'll need to do:
Locate the upstream oxygen sensor and disconnect it from its engine wiring harness connector.
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).
Probe the outer terminals of the O2 sensor's connector with your multimeter's test leads
Remember, you're testing the engine wiring harness O2 sensor connector (which has female terminals) and not the connector of the O2 sensor itself.
With the Key On Engine Off (KOEO), your multimeter should register 10 to 12 Volts DC.
Let's take a look at your test results:
CASE 1: Your multimeter registered 10 to 12 Volts DC- Good, since this confirms that the rear oxygen sensor's heater element is getting power and ground.
The next step is to verify that the heater's resistance is within specification. For this test, go to TEST 2: Testing The Heater Element's Resistance.
CASE 2: Your multimeter DID NOT register 10 to 12 Volts DC- The most likely cause is that power is missing due to a blown fuse or a short (or open) in the wiring. You'll need to check fuse #9 (15 amps) in the fuse box and make sure it's not blown.
If the fuse is OK, your next step is to find out why this battery power (or ground) is missing using a wiring diagram.