Front O2 Sensor Heater Test -P0135 (1995-1999 1.6 Nissan Sentra)

TEST 2: Testing The Heater Element's Resistance

This last test involves checking the heater's internal resistance with your multimeter in Ohms mode.

In case you're wondering, you don't need to remove the O2 sensor to test it.

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 outer 2 male terminals identified with the numbers 1 and 3 in the illustration above of the O2 sensor connector itself (not the engine wiring harness O2 connector).

2. 2

   With your multimeter in Ohms mode, probe terminals #1 and #3 of the O2 sensor itself.

3. 3

   If all is OK, you should see about 2.3 to 4.3 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 front O2 sensor's heater resistance is within specification. This test result tells you that front oxygen sensor's heater is OK.

CASE 2: Your multimeter showed an open circuit (OL). This confirms that the upstream O2 sensor's heater element is fried.

You can correctly conclude that the upstream O2 sensor needs replacement if you have:

Here are some more specifics: Since you have:

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

Replacing the upstream O2 sensor with a new one will solve the P0135 trouble code lighting up the check engine light (CEL).

More 1.6L Nissan Tutorials

You can find a complete list of tutorials in this index: Nissan 1.6L Index Of Articles.

Here's a small sample of the 1.6L Nissan tutorials you'll find in the index:

• How To Test The Idle Switch (1997-1999 1.6L Nissan Sentra).
• How To Test Engine Compression (1.6L Nissan).
• How To Troubleshoot A No Start (1.6L Nissan).
• How To Test The TPS (1997-1999 1.6L Nissan Sentra).
• Mass Air Flow (MAF) Sensor Test Nissan Sentra 1.6L (1995-1999) (at: easyautodiagnostics.com).