Air & Fuel Mixture ControlOBD2 Codes

P0135 – Meaning, Causes, Symptoms, & Fixes

Reading Time: 3 minutes


Code P0135 Definition

O2 Sensor Heater Circuit Malfunction (Bank 1 Sensor 1)

What Does Code P0135 Mean?

Heated oxygen sensors contain heating elements to help them get to operating temperature quickly in order to minimize the amount of time spent in open-loop operation (A fixed rich mixture). Code P0135 occurs when the powertrain control module tests the upstream heated oxygen sensor’s heater circuit on Bank 1 and detects a short in the circuit or excessive resistance in the heater circuit.

What Are The Symptoms Of Code P0135?

  • Check Engine Light is on
  • Decreased fuel economy
  • Rough running engine

What Is The Cause Of Code P0135?

  • Faulty Pre-Catalyst oxygen sensor
  • Faulty wiring/connections
  • Short or open ground in the wiring
  • Blown Fuse
  • Engine coolant temperature sensor is not operating correctly
  • Faulty Power Control Module

How Serious Is Code P0135? – Moderate 


This Diagnostic Trouble Code (DTC) does not need to be attended to immediately, but this DTC could result in more costly repairs in the future.

Code P0135 Common Diagnosis Mistakes

Replacing the oxygen sensor when the issues could actually lie in wiring/connections.

Tools Needed to Diagnose Code P0135:

How To Diagnose And Repair Code P0135:

Difficulty of Diagnosis and Repair – 2 out of 5

This video does a great job of outlining the diagnostic process for P0135, but we have provided an overview below:

  1. Do a road test. Clear the fault codes with your FIXD sensor and drive around to verify failure. If the Check Engine Light comes back on continue to Step 2.
  2. Check that the O2 sensor is getting battery voltage by using your multimeter. Consult your vehicle repair manual to locate the harness connector for the bank 1 sensor 1 O2 sensor. Disconnect the harness connector and turn the ignition to the on position (do not crank car). Test the O2 sensor for proper voltage with a multimeter using the instructions from your vehicle’s repair manual. (if no power check fuse)
  3. Visually check the electrical connections, wire harness, and metal tabs in terminals for any damages. Damages found? Replace O2 Sensor – Clear code. No damage? Continue on to Step 4
  4. Check the engine ground – Consult your repair manual to find where the engine ground is located. Corrosion? Loose connections? Remove corrosion/tighten and restart the diagnostic process
  5. If all of these tests are good, replace the bank 1 sensor 1 O2 sensor.* 

* Still having trouble finding the issue with your vehicle? Please take it to the nearest auto shop so that they may check other possible issues, including the Engine Control Module (ECM).

Estimated Cost of Repair

For error code P0135, one or more of the below repairs may be needed to solve the underlying issue. For each possible repair, the estimated cost of repair includes the cost of the relevant parts and the cost of labor required to make the repair.

  • Oxygen Sensor $200-$300
  • Fuse $5
  • Wiring repair/replacement $100-$1000

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  1. Will monitor as suggested and respond per your suggestions.

  2. FixD works great! Once I got the App installed right and registered, it showed the potential reason on the check engine light, and how to diagnose sensor. In a few minutes you know what to do, where and how. Love it!

    1. Love it cool

  3. Changed O2 sensor.

  4. Did that fix the problem?

    1. Changed all 4 on vehicle and still brings up the same 2 codes

  5. How can you tell if is the upper Left or r ugh this downstream or or the Lower right or left downstream 02 heater sensor since it only gives code P035

    1. It will.display a 4 digit error code not 3

      1. your product is awesome keep up the great work the savings you help with are out of this world
        Great Job and thank you

        1. Thank you so much for the kind words and for using FIXD! 🙂 Happy and safe driving!

  6. Got lucky no parts needed. Had a leak at the exhaust / manifold gasket ring. Loosened the pipe and all is good. Worth taking a extra look

  7. Question- I have a straight 6 and have this error code. I havn’t yet looked at the engine but It says bank one sensor one so how to know exactly which part to order as it’s saying the same number on straight 6 or V 6 and I know they are different.

    1. No they are the same. Bank 1 code for V6 is the same as I6, which only has one bank.

  8. No, they’re not different. Bank 1 code of a V6 is the same as the I6 code.

  9. Another useful diagnostic is to check the battery. If battery hasn’t got sufficient cranking amps, this error can appear. Car will run a bit rough, some makes/models will run a few degrees warmer though not usually enough to set off any more warnings.

  10. installed a new oxygen sensor engine light came off turn engine off started back up engine light came back on now what

  11. Thank you L. Mac! Already knew my battery needed replacement and you saved me a lot of unnecessary work trying to find the source of this code.

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