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P0155

Low Severity

O2 Sensor Heater Circuit (Bank 2, Sensor 1)

Emissions System

What Does P0155 Mean?

Heater failure in the upstream O2 sensor on bank 2.

Common Fix

Replace O2 sensor

Estimated Cost (DIY)

$30 - $100

Symptoms

  • ⚠️Check engine light
  • ⚠️Slightly worse fuel economy cold
  • ⚠️Failed emissions

Common Causes

Failed heater elementlikely
Blown fusepossible
Wiring issuepossible

How to Diagnose P0155

  1. 1Check O2 heater fuse
  2. 2Measure heater resistance
  3. 3Inspect wiring
  4. 4Replace sensor

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Frequently Asked Questions

Is the bank 2 O2 sensor different from bank 1?
Often yes β€” bank 1 and bank 2 upstream sensors may have different part numbers due to wire length or connector style.
Can I use universal O2 sensors?
Yes, but you must splice the wires correctly. Direct-fit sensors are easier and more reliable.

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