P0135 Honda 1.6L – Test a Civic 02 Sensor

This article is meant to assist you in resolving the OBDII P0135 Honda DTC Trouble Code, which relates to your primary oxygen sensor or Honda Civic 02 Sensor. The proper terminology for this trouble code is O2 Bank 1 Sensor 1 Heater Circuit Efficiency in your 1995-1999 1.5 liter or 1.6 liter SOHC Honda Civic.

This primary oxygen sensor is required for your ECU to operate closed loop or part throttle. Because your 02 sensor is not transmitting the data the ECU expects, and is not functioning properly, your Malfunction Indicator Lamp (MIL) light is on.

Typically what causes this P0135 Honda trouble code is a fault in the oxygen sensor or a short in the heating element. I’ll be showing you how to test each individual wire as well as the wiring in your vehicle to determine what the root cause is. Today’s vehicle is a 1997 Honda Civic with the D16 1.6 liter VTEC engine.


Symptoms of a Failed Primary 02 Sensor


  • Sluggish throttle
  • Poor vehicle response
  • Belching black smoke
  • Overly rich ( excessive gas in exhaust )

What are we testing exactly?


The job we are performing is to test your 02 sensor in your Honda Civic, to determine if it’s receiving power and that there’s no breaks from the engine harness to the ECU in question. To test your 02 sensor, you will need to locate the 02 sensor which is screwed into the primary exhaust header of your engine.

Open your engine bay and look in your header system for this 02 sensor and more importantly the wire harness coming from the sensor itself.

As with all of our writeups, always take the proper precautions when working on your car. Never probe the front of your engine harness or any electrical connector, as you can compromise the plastics that clip into place.

How to Test your 02 Sensor


To test your 02 sensor you will need to put the key to the “ON” position, but do not start the engine. Locate your oxygen sensor and unplug the engine harness from the flying loom.


This is a standard 4 wire heated oxygen sensor, and it’s primary job is to detect the amount of unburnt fuel in your exhaust stream. By analyzing the gas in your air, your Honda ECU can then correct the fuel delivery to compensate.

With the 02 sensor unplugged, you will be testing the ENGINE HARNESS side of the plug for power and low reference (GROUND) signals. After unplugging the connector, examine the diagram below for the 1996 Honda Civic oxygen sensor wiring pinout.


Make sure you are looking at the engine harness side of your primary Civic 02 Sensor harness. Now using your multimeter, place the black probe lead to the negative terminal of your battery. Now put the red probe to PIN 3, which should be a black wire with yellow stripe. This is switched power from the ECU, you should have power at this pin with the key set to the “ON” position.

If you have power here, next you will be testing for the low signal reference, or ground. This ground is supplied by the P2P or P28 ECU in your Honda Civic. PIN 4 which should be a black wire with white stripe is the 02 sensor heater ground, put the black lead to this pin, and the red lead to your battery terminal to check for ground.

If you have power and ground at the terminals of your engine harness, this means that there’s power and ground at the oxygen sensor. Chances are your heater element is fried, so let’s check that next.

Put your multimeter in OHM mode and you will be testing PIN 3 and PIN 4 for the proper resistance. Honda calls for this resistance to be within 10-40 Ω, put the black lead to pin 3 and the other lead to pin 4 and measure resistance between the pins.

If the resistance between these two pins is not between this range, your front oxygen sensor is bad and must be replaced. The part number for this replacement is 36531-P0G-A01, but it can also be carried under the following part numbers:

Honda Part numbers for the front primary 02 sensor in a 1995-2000 Honda Civic : 36531-P8E-A01, 36532-P2E-A01, 36532-P2E-A51, 36532-P30-A01, 36532P5A003, 36532P5G003, 36532PR7A01, 36532-PR7-A02, 36532-PR7-A11, 36532-PR7-J01, 36532-PR7-J02, or 36532-PY3-003.

Have any questions about this guide on clearing the P0135 Honda trouble code? leave them for me below!


  1. John

    At last! Something clear I can unsdaetrnd. Thanks!

    1. John Huh (Post author)

      Thanks John! Glad it helped you out sir!

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