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I own a 2002 Chevy Blazer 4-door with the 4.3 Vortec. I have been having issues with the O2 Sensors. I purchased it used about 5 months ago. I was getting a heater circuit code for Sensor 1 Bank 1. I replaced it and all was fine. Then I got a heater circuit code for Bank 1 Sensor 2 shortly after replacing the other Sensor. This Blazer has 3 Oxygen Sensors on it. I have replaced all 3 O2 Sensors and now I am getting a Sensor 2 Bank 1 code again only this time I got a heater Circuit code and No Single code. I started getting performance issue as well. I cleared the codes and it is running fine again but, the codes came back again for the Sensor 2 Bank 1 code again heater Circuit code and No Single. The codes came back after only a short drive. I believe this is the one after the cat. Is it possible I have a defective new O2 Sensor or something more serious? I also want to mention the fuel pump is making a really high pitch whine and the sending unit has a bad resistor casing fuel gauge issues. It is hard to start after it has been sitting for a while. Have to turn it over for a few more seconds and is especially bad first thing in the morning. I feel that I have low fuel pressure but haven’t bought a gauge yet to test the pressure. I read that someone has a somewhat similar issue with a no start and same O2 Sensor code and ended up being a bad fuel pump. Does anyone know if it is possible to get this O2 Sensor; Sensor 2 Bank 1 heater Circuit code and No Single code from week fuel pressure? I was also thinking the fuel pressure regulator on the Spider injector for the hard starts. I am hoping it isn’t a wiring problem. This is starting to get expensive. The Blazer Has 103k on it and I just had to put in a darn rebuilt transmission because the sun-gear went causing loss of 2nd, 4th and revers. I attached a picture of the O2 Sensor Diagram. Any feedback would be very greatly appreciated.
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I don’t believe low fuel pressure will give you o2
heater circuit circuit code. You would most likely
get a lean code.check your fuses for the o2 heater
circuit.also check the o2 heater circuit for power
and ohm the heater circuit.what brand o2 are you using?Thanks for the info! I check the fuses and they look fine. I don’t have the Blazer home with me right now so I can’t go any further with it today. I installed “Denso” brand O2 sensors which is the same as was in there. Most of the parts are Denso unlike my 97 Blazer where everthing is AC-Delco. Probably the reson I am having these problems. As far as I know my 97 Blazer has all the orginal O2 Sensors with 140k.
So whtat Do I need to do to ckeck for voltage on the wires?
The heater circuit wires need 12v. With the key
on engine off check the heater circuit wires for the
12vProblem solved! The wire harness that runs from the ECM down the right side on the frame to pre-cat and post car O2 sensors got burned against the hot exhaust. spliced and soldered in new wires into the effected area of the hardness. All is well, O2 sensor responding properly now and no more check engine codes. Completed drive cycle and still working great. Thanks everyone for info
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