Air & Fuel Mixture ControlOBD2 Codes

P0155 – Meaning, Causes, Symptoms, & Fixes

Reading Time: 2 minutes


Code P0155 Definition

O2 Sensor Heater Circuit Malfunction (Bank 2 Sensor 1)

What Does Code P0155 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 P0155 occurs when the powertrain control module tests the upstream heated oxygen sensor’s heater circuit on Bank 2 and detects a short in the circuit or excessive resistance in the heater circuit.

What Are The Symptoms Of Code P0155?

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

What Is The Cause Of Code P0155?

  • 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 P0155? – 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 P0155 Common Diagnosis Mistakes

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

Tools Needed to Diagnose Code P0155:

How To Diagnose And Repair Code P0155:

Difficulty of Diagnosis and Repair – 2 out of 5

This video does a great job of outlining the diagnostic process for P0155, 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. If the Check Engine Light comes back on continue to Step 2.
  2. Check to make sure the O2 sensor is getting battery voltage by using your multimeter. Consult your vehicle repair manual to locate the harness connector for the bank 2 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 2 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 P0155, 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. What about u1501 code?

    1. Hi James! We really appreciate you reaching out! “U” indicates it is a network code. However, when codes start with U1XXX, it indicates they are reserved for manufacturer specific codes which we do not have access to at this time. A manufacturer specific scan tool is required to diagnose these types of codes.

  2. When the repair refers to a “bank,” what is that telling me?

    1. Patrick “bank” is referring to one side or the other of the engine bank one 1 would be left side of engine bank 2 is right side of engine thats looking at the engine while in the driver seat so from the front of the car it would be opposite hope that helps.

  3. I love you

  4. What is po154 code?

  5. I just replaced this PO155 bank 2 Oxygen sensor last year! So is this normal for the sensors to keep going out like this? On a 2001 Nissan Maxima? Frustrating

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