P0135 – Meaning, Causes, Symptoms, & Fixes

Code P0135 Definition

O2 Sensor Heater Circuit Malfunction (Bank 1 Sensor 1)

Code P0135 Meaning

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.

P0135 Symptoms

  • Check Engine Light is on
  • The engine may be running rough
  • Decreased fuel economy
  • Rough running engine

P0135 Causes

  • Faulty rear most oxygen sensor
  • Faulty wiring/connections
  • Short or open ground in the wiring
  • Engine coolant temperature sensor is not operating correctly
  • Faulty Power Control Module

Code P0135 Severity – 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 the catalytic converter, wiring/connections, or an exhaust leak before the oxygen sensor.

Code P0135 Diagnosis Steps

  • Tools Needed to Diagnose:

How To Diagnose P0135
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 a failure.
    1. 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.
    1. Consult your vehicle repair manual to locate the harness connector for the O2 sensor
    2. Disconnect the harness connector and turn the ignition to the on position (do not crank car)
    3. Test O2 sensor for proper voltage with a multimeter using the instructions from your vehicle’s repair manual.
  3. Visually check the electrical connections, wire harness, and metal tabs in terminals for any damages
    1. Damages found? Replace O2 Sensor – Clear code
    2. No damage? Continue on to Step 4
  4. Check the engine ground – Consult your repair manual to find where the engine ground is located
    1. Corrosion? Loose connections? Remove corrosion/tighten and restart the diagnostic process


* 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).

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Comments 10

Charlie Helms

August 5, 2018

Will monitor as suggested and respond per your suggestions.

sandie wisman

August 11, 2018

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!

John Jee

September 13, 2018

Changed O2 sensor.

Glenn Bourbon

November 1, 2018

Did that fix the problem?

Johnny Elixson

May 17, 2019

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


June 7, 2019

It will.display a 4 digit error code not 3

Lawrence Cline

June 9, 2019

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


June 19, 2019

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.

Mike Castillo

June 26, 2019

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

Mike Castillo

June 26, 2019

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

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