Hello! I am new to the forum but long term "Blazer" addict. My previous Blazer was a 1987 that I just replaced with a 2000 last year. The 87 was faithful, reliable and never failed to start! This new (to me) has endured a few issues, all of which I repaired but the most frustrating is it's P0155 code. I have replaced EVERY O2 sensor in it, cleaned the electrical connections, checked fuses, wires, changed out all filters and finally asked it just to stop (Duh doesn't work). I even had my Husband buy me the ODBII code reader unit for an anniversary gift to "ease" the workload. Consistently same code every second drive, never thrown any other code - how in the Blazers do I fix this?! Every morning on the way to work I clear the code only to have it return on my way home. It's driving me mad! I thank any and all who can give me help. Cheers

 

Have a read through this thread:
P0155 - Heated Oxygen Sensor Heater Circuit (bank 2, sensor 1)

This code states that there is a problem with the heater circuit on the B2S1 (passenger side upstream) sensor.

 

I have done much research on this before... it's an ongoing issue! What I gain from your thread share is that now I must test my voltage... crikey slightly outta my league I think. I was hoping it would have been something a bit easier to tackle. I thank-you greatly for your time in this matter. I really had hoped that by changing out all the O2 sensors the problem would be fixed but as soon as ambient air temp dropped below 20 degrees it came back. Grr! Thanks again.