Brand new to this forum so hopefully this gets posted correctly/. I just bought my father in=laws 1998 Chevy blazer 4x4 4.3 engine with 260000 miles. My wife complained about it taking longer than normal to start when it was cold. I decided maybe it was the fuel filter. started great for 3 days. then check engine light came on and it cranks longer than normal. Took it to auto zone for there free diagnostics scan. guy did not tell me the code but said it was bank 1 sensor 3 o2 sensor. pulled it replaced it light is still on. This worries me because I had a 98 s-10 four banger with the same code. changed o2 sensor turned out to be 800 dollar catalytic convertor was the problem. (Funny I only paid 20 bucks for the 4 banger sensor.) Anyway what else could cause this o2 sensor code to come on. Could I have done something wrong with the fuel filter? check engine light never came on till I changed the filter. I havnt done anything else to it but fuel filter and 02 sensor. Thanks for the help guys.

 

Really need the specific code to help beyond telling you that the problem wasn't the sensor. Could be a failing catalytic converter, wiring problems, etc. The code will get you to a diagnostic procedure which will lead you to the true source of the problem.

 

Ok wife is out with it right now. When she gets home i will have her take it back to Autozone and get me the code. A guy told me to unhook that sensor totally to see if it changed anything and yes it did. idled like poo. So after that I was sure it wasnt the sensor but it was too late. I already changed it. But when she gets here I will send her for the code. Thanks for the looksy though.

 

The B1S3 sensor has nothing to do with engine operation and is only a catalyst monitoring sensor (it's the post cat sensor). A malfunction in this sensor (if the sensor or wiring is at fault) will have no effect on engine operation of the engine nor should disconnecting this sensor. Are you sure you are working with the right sensor? Your truck should only have 3 sensors, 2 upstream that are located in the y-pipe between the exhaust manifolds & the 'y' in the y-pipe on either side of the engine (B1S1 - driver & B2S1 - passenger) and then the B1S3 should be after the catalytic converter.

 

Best I can tell by the diagram is there is 4. I could be wrong. One on each manifold. One above the y-pipe and one after the convertor. I really need her to get home with this thing so I can get it hooked up for that code. I know enough about cars but, when it comes to o2 sensors I get all blurry eyed. My diagram shows B1S3 after the converter. That is the one I broke my loan a tool program sensor wrench removing. I will post what I find after I get the correct info for you guys. Thanks again.

P0147 02 Sensor Heater Circuit Malfunction (Bank I Sensor 3). This is the code the guy gave her. I called her and she dropped her shopping to do that for me. So now I'm more lost than before. What is the heater circuit.

Well I poked around on google and I found a sight that says it could be a fuse in the heatinfg system. Any idea where that would be? or a faulty o2 sensor. gotta get it home here to be able to solve this one i guess.

 

Quite often the problems such as yours are wiring related. You've already replaced the sensor so check upstream in the harness, toward the PCM, starting with the connector

 

Would this be the possible problem of the extra cranking to start? Or is there more than one issue going on here? Why did the check engine/o2 sensor problem occur after I changed the fuel filter. The sensor is nowhere near the filter. I doubt I moved unplugged any wires.

 

Well here is my update. Unhooked battery for like 2 hours. check engine light is out but for how long? who knows? It starts right up like a new car too. no more 7 second starts. 3 seconds and shes running. I had not done this after changing sensor. May of bee fixed all along but not cleared yet. I will update you wjether it comes back on or not. Thanks foir all the help guys.

 

Alright guys. does anyone know where this fuse is for the o2 heater? I found a page for a 97 blazer saying its eng1 but is that the only fuse and also is it the same as on the 97 for the 98. I know the fuse block appears different. A good schematic would help too. Thanks guys.

 

I am pretty sure that I have posted the 97 engine diagrams before, but I can't effectively search, copy, & paste from my phone so I'll edit this once I get to my pc this morning.