P0135 Code – Meaning, Causes, Symptoms (& How To Fix)

P0135 Code

If you are dealing with the P0135 code and trouble with your car, you want to get it fixed quickly. However, it can be difficult figuring out exactly what is wrong.

That’s why I put together this handy guide, showing you the meaning behind the P0135 trouble code and what can cause it. You will also see the symptoms it causes, and I will outline some of the top fixes. 

Code P0135 Definition

P0135 – Oxygen O2 Sensor Heater Circuit Malfunction (Bank 1, Sensor 1)

What Does the P0135 Code Mean?

The P0135 code indicates that the heated oxygen sensor (Bank 1, Sensor 1) current is lower or higher than its factory specifications. It’s a generic trouble code that can be found with many automotive brands. 

The O2 sensors in the vehicle contain heating elements which help to reduce the time needed to reach ideal temperatures. If there’s a delay occurring between its startup and the activity of the sensor, the PCM will set a code. 

READ MORE: Bank 1 vs Bank 2 – Sensor 1 & 2 (Locate O2 Sensors Fast & Easy)

P0135 Trouble Code Symptoms

The reason that you found the P0135 trouble code is because the Check Engine Light first came on. This is the most common symptom, but it’s not the only one that can occur.

Here are a few other symptoms you might notice.

Causes of the P0135 Code

Most commonly, the problem relates to the oxygen sensor itself. Whether it needs to be replaced or there is a connection error can only be determined after proper diagnosis. Still, there could be other causes, such as what’s listed here.

How Serious is the P0135 Code?

Medium – If the engine is continuing to run without any issues, you might be tempted to continue driving. You could get away with driving home or to the local shop, but you probably shouldn’t go much further. 

Instead, it’s best to have the fault checked out right away. If you don’t, it’s possible to cause more engine damage, which can cost you additional repair bills. 

What Repairs Can Fix the P0135 Code?

I outline the best way to figure out what’s wrong with your car. You should go through these steps first to determine what needs to be repaired. However, here are a few of the most common repairs that fix your situation.

  • Repair damaged wiring/connectors
  • Replace burnt fuse
  • Replace oxygen sensor
  • Update/replace PCM

Common P0135 Diagnosis Mistakes

The most common way to handle the P0135 trouble code is to replace the oxygen sensor. While this seems most logical, you don’t want to replace it unless it is defective. 

Instead, you want to walk through the complete diagnosis to ensure your problem doesn’t lie with a simple connection, fuse or wiring fault. Otherwise, you could replace an oxygen sensor and still notice the same problem. 

How to Diagnose the P0135 Trouble Code

It doesn’t take a lot of effort to troubleshoot the P0135 DTC. You can complete the same steps as a professional, even if you don’t have a lot of experience or tools.

Here are some basic guidelines to follow.

  1. Check engine codes with your scanner. Clear the codes and go for a drive to see what comes back.
  2. Look at the electrical connections. Inspect the wiring harness, wiring and metal tabs found in the terminals. If you notice any damage, this should be dealt with first.
  3. Inspect the engine ground connection. You can find the location in your service manual. If there is corrosion or you have a loose connection, you need to repair the problem before moving on. 
  4. Check how much battery voltage the oxygen sensor is getting with a multimeter. To do this, disconnect the harness connector to this oxygen sensor and turn the ignition on without starting the motor. Test the voltage to confirm that there’s enough power. Check the fuse or wirings if you find any issues with the voltage.
  5. If you can’t find any other issue, you may replace the oxygen sensor. 

After these steps, other issues should only be trusted to a professional mechanic. You don’t want to work with the PCM if you don’t have the experience. You can take your vehicle to a local shop for a PCM update or replacement if needed. 

Estimated P0135 Repair Cost

Once you’ve determined what the cause of the P0135 trouble code is, you want to know how much you are going to spend to repair it. Here are a few estimates to consider, all of which reflect labor and parts. 

  • Repair damaged wiring/connectors – $50-$550
  • Replace oxygen sensor – $250-$650
  • Replace fuse – $1-$10
  • Update/replace PCM – $250-$2,500

Mechanics Tips about the P0135 Code

As with all vital engine trouble codes, you may notice other DTCs that seem closely related to this one. While they might be different, you could also notice these, which have some of the same causes, symptoms and repairs. 

  • P0141 – Sensor Heater Circuit Bank 1 Sensor 2
  • P0161 – Sensor Heater Circuit Bank 2 Sensor 2
  • P0135 – O2 Sensor Heater Circuit Bank 1 Sensor 1
  • P0155 – O2 Heater Circuit Bank 2, Sensor 1

To get clarification between the codes, you can research them on our site. Otherwise, you want to seek more help from your mechanic.

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Magnus Sellén
Written by:

Magnus, the founder and owner of Mechanic Base, is an experienced car mechanic and diagnostic technician with over a decade of experience in advanced car diagnostics and troubleshooting. By holding certification as an Automotive Diagnostic Technician, Magnus's technical expertise is widely recognized and forms the bedrock of the trusted advice shared here. His background is further enriched by his time as a motorsport (drifting) driver for Sellén Drifting, which reflects a deep passion and extensive involvement in the automotive industry. Magnus is committed to using his extensive knowledge and enthusiasm for cars to provide reliable, accurate and practically sound advice.

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