Air & Fuel Mixture ControlOBD2 Codes

P0155 – Meaning, Causes, Symptoms, & Fixes

What Does Code P0155 Mean?

  • P0155 definition: O2 Sensor Heater Circuit Malfunction (Bank 2 Sensor 1)
  • Issue Severity: MODERATE– Extended driving with this code can cause internal engine damage.
  • Repair Urgency: Get this code fixed as soon as possible.
  • Diagnosis: It is important to complete the entire diagnostic process when diagnosing the P0155 code. This DTC can be triggered by a faulty oxygen sensor and/or wiring.

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.

P0155 Causes

  • 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

P0155 Symptoms

  • Check Engine Light is on
  • Engine running rough
  • Decreased fuel economy

How Do I Fix Code P0155?

With a P0155 code, the first step is to get it properly diagnosed to figure out what is causing the malfunction in the oxygen sensor system. Using the live data function of the FIXD sensor and app allows you to read and analyze engine data to properly diagnose a P0155 code.

If the sensors are all reading correctly and you’re not comfortable further diagnosing this issue at home, we recommend finding a RepairPal-certified shop to pinpoint the problem and give an accurate estimate for repairs. 

These shops can not only help you figure out what’s going wrong before you waste time and money on the wrong parts, but they also offer a minimum 12-month, 12,000-mile warranty and stand behind all their estimates with guaranteed fair pricing.

> Find a RepairPal Certified Shop Near You

How Much Does It Cost to Fix Code P0155?

If you take your car to a shop for diagnosis, most shops will start with an hour of “diag time” (the time spent in labor diagnosing your specific issue). Depending on the shop’s labor rate, this typically costs somewhere between $75-$150. Many, if not most, shops will apply this diagnosis fee to any required repairs if you have them perform the repairs for you. From there, a shop will be able to give you an accurate estimate for repairs to fix your P0155 code.

Possible Repair Costs for P0155

When it comes to making repairs associated with the P0155 code, 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

DIY Steps to Diagnose Code P0155

If you’d like to try to fix code P0155 at home without throwing money at parts, you’ll want to follow the steps below for proper diagnosis. Complete diagnosis may require some specialized equipment beyond what the FIXD Sensor can provide, but the biggest challenge for this repair is that internal engine issues could be the root cause of this code. As such, this diagnosis and repair should not be attempted by beginner DIYers. 

DIY difficulty level: Beginner

This repair can be attempted by beginner DIYers.

Tools/parts needed (our top picks from Amazon):

STEP 1: USE FIXD TO ENSURE NO OTHER ENGINE CODES ARE PRESENT.

Scan your vehicle to verify P0155 is the only code present. If other codes are present, they must be addressed first.

STEP 2: INSPECT O2 SENSORS AND WIRING. 

Visually check the electrical connections, wire harness, and metal tabs in terminals for any damages. If any damage is found, replace the oxygen sensor.

STEP 3: CHECK OXYGEN SENSOR(S) WITH MULTIMETER.

Consult your vehicle repair manual to locate the harness connector for the O2 sensor, and using your multimeter, check to make sure that the sensor is getting battery voltage. Disconnect the harness connector and turn the ignition to the on position (do not crank car). Test O2 sensor for proper voltage with a multimeter using the instructions from your vehicle’s repair manual. 

STEP 4: CHECK THE ENGINE GROUND.

Consult your repair manual to find where the engine ground is located. Look for corrosion or a loose connection, and repair as necessary. 

STEP 5: CONSULT A PROFESSIONAL.

If at this point the vehicle is still setting the same code, you may have a more serious problem with your car’s oxygen sensor system, and you should bring the vehicle to a certified shop to have further diagnostic work performed.  

Common P0155 diagnosis mistakes

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

Still Need Help Fixing Code P0155?

If you’ve followed the steps above and are still experiencing issues with the oxygen sensor system and code P0155, please contact the FIXD Mechanic Hotline if you’re a FIXD Premium subscriber or find a RepairPal certified shop near you to get the right repairs at a fair price.

Jeffrey-Ross

Lifelong automotive enthusiast with a soft spot for offroading. Wrencher turned writer, but I still love to tinker on just about anything with an engine. Dream car: tie between a ‘71 Hemi ‘Cuda and a ’91 GMC Syclone. #GirlDad #SaveTheManuals

Jeffrey N. Ross
Lifelong automotive enthusiast with a soft spot for offroading. Wrencher turned writer, but I still love to tinker on just about anything with an engine. Dream car: tie between a ‘71 Hemi ‘Cuda and a '91 GMC Syclone. #GirlDad #SaveTheManuals

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8 Comments

  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

  6. good day every one…. new here, any one could help me to know what exactly ground voltage will produce by the ecu to the oxygen sensor heater of nissan xtrail thank you very much who could help me….

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