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Dan, Technician
Category: Chevy
Satisfied Customers: 23492
Experience:  Independent Shop Experience, 2 Year Automotive Diploma, & Access to Information Database
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Blazer: an error code (Po155, 02 sensor heater circuit malfunction)

Resolved Question:

i have recieved an error code (Po155, 02 sensor heater circuit malfunction) on my 2002 chev. blazer. is this an "easy" fix, plug and go or more than my weekend mechanic skills can handle?
Submitted: 7 years ago.
Category: Chevy
Expert:  Dan replied 7 years ago.

Yes it is very easy. You need to go to your local parts store and buy a special socket so you can removeinstall oxygen sensor without damaging it. Here are instructions to replace. Let me know if you have questions. Thanks


Heated Oxygen Sensor (HO2S) Replacement Bank 2 Sensor 1

J 39194-B Oxygen Sensor Wrench


CAUTION: Refer to Vehicle Lifting Caution in Service Precautions.

  1. Raise the vehicle. NOTE: Refer to Heated Oxygen and Oxygen Sensor Notice in Service Precautions.
  2. Disconnect the connector (1) for the HO2S. NOTE: Refer to Excessive Force and Oxygen Sensor Notice in Service Precautions.
  3. Remove the HO2S (2) using a J 39194-B.


IMPORTANT: A special anti-seize compound is used on the heated oxygen sensor (HO2S) threads. The compound consists of liquid graphite and glass beads. The graphite tends to burn away, but the glass beads remain, making the sensor easier to remove. New, or service replacement sensors already have the compound applied to the threads. If the sensor is removed from an engine and if for any reason the sensor is to be reinstalled, the threads must have anti-seize compound applied before the reinstallation.

  1. Coat the threads of the oxygen sensor with anti-seize compound GM P/N(NNN) NNN-NNNN if necessary. NOTE: Refer to Component Fastener Tightening Notice in Service Precautions.
  2. Install the HO2S (2) using a J 39194-B. Tighten Tighten the sensor to 42 N.m (31 lb ft) .
  3. Connect the HO2S harness connector (1).
  4. Lower the vehicle.
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