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Hey everyone- I have a REAL pain on the brain problem maybe someone can help with.
I pulled and replaced a 4.3 engine in my 97 blazer myself with a reman. The “y” pipe was junk so I replaced it along with all the O2 sensors. 1- downstream and 3-upstream. Now before I pulled the old engine nothing was wrong with emissions, not even a pending trouble code on my actron scanner. I had a rod bearing go out so thats all that was wrong.Now when I replaced the “y” pipe with a new WALKER UNIVERSAL PIPE- it was missing a thread hole for one of the o2 sensors,the one where both banks come togather,I guess some blazers were made without that one. So I wire welded a new thread collar in with my wire welder and the o2 sensor threaded right in.I even pulled it back out to make shure it did not bottom out.All looks well,but now when i start it 2 PENDING CODES are on the scanner. P1133- H02S SENSOR 1 INSUFFICIENT SWITCHING. And the second code is P1153-H02S 2/1 INSUFFICIENT SWITCHING. Where I am stuck is I dont have the book info to know what sensor this is? Does 2/1 mean upstream for cylinder bank 2? And bank 2 should be passenger side- right? I just have a hanes manual that does not specify my blazer 02 sensors. ANY THOUGHTS GREAT!
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2/1 means the bank 2 up-stream sensor (not the one after the converter). I would be surprised if your Haynes manual doesn’t have a simple diagram of the engine block with the cylinders numbered, but just in case it doesn’t, you should be able to figure it out like this: On a ‘V’ type engine the left and right banks of cylinders are offset a little, bank 1 is the one that sticks out forward a little more than bank 2. Sometimes it’s tough to tell, I’d take another look at the manual and see if you can find the diagram.
Thanx for the reply- if 2/1 means bank 2 closest to engine, then I was wondering what the 02 sensor after both banks but before the cat would be called? cuz this is the one I wirewelded in, seems tight and no leaks, but you would think that would be the problem.I will check what bank is out the farthest. THANX!
I’m not sure I understand what you are asking. Usually there will be 1 sensor for each bank, located before the catalyst, and then 1 behind each converter.
So, the 2 in front of the converters will be 1/1 and 2/1.
The ones behind the converters will be 1/2 and 2/2.Are you saying you have another in the middle????
yes- there is one sensor for each bank, then one where the banks mix gases together (just before the cat)and then one after the cat. there is only one cat on this blazer. The book talks about there being no sensor after the banks come together. Some research tells me blazer was good for changing their emissions in the middle of a year? I guess thats what I read?
That is bank 1 sensor 2 or 1/2. The one after the cat on your blazer is bank 1 sensor 3. Both of the sensors closest to the engine have a problem, either bad sensors, vacuum leak, or exhaust leak.
Thanx for the reply- that explains alot- so bank 1 has two sensors upstream and bank 2 has one. May I ask how you know both banks closest to the engine have a problem?
If you have a scan tool that shows PID data, look at the pre-cat o2 voltages. They should fluctuate between 0.1 and 0.9v. If they do not, create a vacuum leak and see if the sensors respond. You could also use propane too.
You could also try using a DVOM.
I would do a good visual inspection of the exhaust system checking for any leaks. You could try using a rag in the tail pipe to block the exhaust flow and see if you can see any leaks that way. DO NOT do this for a extended period of time or damage may result. Its just a quick test.
I replaced all 3 upstream sensors new with a new y pipe. The one down stream I replaced new also.All four sensors during a data test on my scanner climb to .8 or .9 like they are suposed to. With a new engine and exhaust installed everything seems tight for leaks. But now I’m wondering if after pulling this engine and reinstalling if I have a vac hose cracked even just a hair line one.Thanks for the possible lead.
Thanx- knowing all sensors are new, new y pipe with all new gaskets, and I pulled engine I am going to look at vac lines.
Reading through I think you’ve got your sensors worked out so I’ll focus on possible causes of the codes. It could be the sensors especially if they came with the new engine. Salvage engines often sit out in the elements so for a sensor to be bad after sitting out in the open it would not be uncommon. Also check for vacuum leaks as you suggested in addition to checking all your hoses and connections to make sure it’s all in there right. Swapping engines is a lot of work, it’s not hard to miss something. Keep us posted.
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