P0135 – O2 Sensor Heater Circuit

P0135 – O2 Sensor Heater Circuit

Your oxygen sensor is a crucial part of your vehicle. By analyzing the air-fuel ratio of your emissions, the oxygen sensor or 02 sensor helps your ECU deliver the right amount of fuel. If your oxygen sensor gets old, or there’s a problem internally with your 02 sensor, the P0135 trouble code can rear its an ugly head.

When you’ve got a check engine light on, you must use a scan tool to retrieve your On-Board Diagnostic trouble code. If your OBDII check engine code comes back as P0135, this can cause serious driving issues with your car or truck.

This OBDII DIY Guide will help you understand your oxygen sensor, and learn how to fix P0135 trouble codes.

What does the P0135 trouble code mean?

The O2 Sensor Heater Circuit OBDII trouble code means that either your oxygen sensor has gone bad, or there’s a problem with your vehicle wiring. The heater circuit of your oxygen sensor provides voltage so that your narrowband air-fuel sensor can function properly.

If your vehicle has a stored P0135 code, your on-board computer will set the vehicle conditions in memory. This will also prevent you from passing smog, and impact your MIL status. Before you go ahead to fix P0135 problems, make sure to verify the code conditions before you advance to the next set of tests.

P0135 Symptoms

  • Poor performance
  • Vehicle may idle or run rough
  • Bad gas mileage
  • Engine dies
  • Black smoke from the tailpipe

Inside the P0135 check engine light

Although most of the time, O2 Sensor Heater Circuit failure stems from your oxygen sensor going bad, it’s not always the sensor. When this happens, you will need to use a multimeter to test the wiring and voltage of your 02 sensor internally.

If you are not able to pass smog due to the P0135 code, you should replace your oxygen sensor first. Not only to pass smog but as a preventative measure so the vehicle won’t remain in a highly polluting operational condition.

Once you have replaced your O2 sensor, your OBD monitors can be cleared which will restore your vehicle function. This will also clear your P0135 trouble code and erase your check engine light. If there is a problem with re-setting the monitors, check out some of these DIY guides to help you root cause the problem.

How to Fix P0135 Guides

Cant fix P0135 trouble code? – Common issues

If you’ve already replaced your oxygen sensor, but your P0135 code isn’t going away, there could be a deeper problem. If you have the proper OBDII scan tool, you must check your code setting. This setting provides real-time driving condition status checks to help you see where the real problem is.

Real-time information sent to your ECU is important because it allows you to read the oxygen sensor values. In order to test the function of your 02 sensor heater, you will need to check for 12-volt signal at the heater wires as well as the ground wires.

Common Causes of P0135 Code

  • Defective Oxygen Sensor/Air Fuel Ratio Sensor
  • Defective Oxygen Sensor/Air Fuel Ratio Sensor Heater Circuit
  • Exhaust System Leak
  • Intake Air System leak
  • Low Fuel Pressure
  • Defective Engine Coolant Temperature Sensor
  • Defective sensor wiring and/or circuit problem
  • PCM software needs to be updated
  • Defective PCM

Polluting Gases Expelled

  • HCs (Hydrocarbons): Unburned droplets of raw fuel that smell, affect breathing, and contribute to smog
  • CO (Carbon Monoxide): Partially burned fuel that is an odorless and deadly poisonous gas
  • NOX (Oxides of Nitrogen): One of the two ingredients that, when exposed to sunlight, cause smog

Common Problems

There can be several P0135 issues when you want to erase your check engine light. Depending on the age of your vehicle, here are just a few of the problems you may encounter.

  • Failed oxygen sensor
  • Damaged 02 wiring
  • Bad ECU

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