Testing a trouble code P0141 on your 1996-1997 Nissan Pick Up is pretty easy. In a nutshell, all that's involved is making sure that the rear O2 sensor's heater element is getting power and ground, then verifying that its resistance is within specification.
In this tutorial I'll show how in a step-by-step way! By the way, you don't need a scan tool since troubleshooting the O2 sensor's heater can be done with a simple multimeter.
Contents of this tutorial:
NOTE: If you need to test the front oxygen sensor's heater (trouble code P0135), see the following tutorial: Oxygen Sensor Heater Test -P0135 (1996-1997 2.4L Pick Up).
Circuit Descriptions Of The Downstream Oxygen Sensor
2 of the 4 rear oxygen sensor wires connect to the oxygen sensing part of the sensor. The other 2 are the ones that feed power and ground to it's heater.
The wires of the engine wiring harness connector are color-coded and this will help us identify which two supply power and ground (to the heater).
In the table below, you'll find the color of the wires and a brief description of the 4 wires of the rear oxygen sensor's engine wiring harness connector. This connector has female terminals while the connector on the rear oxygen sensor itself has male spade terminals.
NOTE: The illustration I'm using throughout this tutorial is of the connector on the rear oxygen sensor itself.
Here's a brief description of the 4 wires of the front oxygen sensor:
|Downstream Oxygen Sensor Pinout
(1996-1997 2.4L Nissan Pickup)
|1||GRN/RED||Heater Ground (-)|
|3||GRY||O2 Signal Ground|
|4||WHT||Heater Power (+)|
TEST 1: Verifying Power And Ground
To find out if the rear oxygen sensor's heater is bad or not, we'll start off by checking the basics: power and ground to the heater.
Now, to get into more specifics: The green with red stripe (GRN/RED) wire (of the engine wiring harness connector) is the one that feeds the rear O2 sensor's heater with power (12 Volts).
The white (WHT) wire (of the engine wiring harness connector) is the one that feeds the heater with ground (this ground is provided by your Nissan Pick Up's PCM).
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 two indicated wires of the engine wiring harness sensor connector.
OK, this is what you'll need to do:
Locate the downstream 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.