I'm curious more than anything. I know a lot of you guys run this motor in your rigs and drivers. We've had a bunch of 03+ trucks coming in with codes. Some run ok, some run like ass. You pull the code and get P030x misfire codes almost always and more and more now we're seeing the P1133 codes coming in with them. Now the first one kicked my ass. Misfires on 1, 3, 5, and 7 constantly with no intake leaks and O2 values that seemed normal enough for a misfiring truck. It was only by shear luck that we got it to run well and then power locked it. Everything was normal the first time I hit the gas. I hit the gas again and everything is normal. I hit the gas the third time and it sounded like pistons were swapping holes. I looked down at the Tech II and B1S1 was laying flat on dead lean. STFT jumped to 53% and the thing damn near flooded out.

So...we replaced the sensor and sent it down the road. A week later it was back, this time for B2S1. We replaced the sensor and pressure tested the cooling system to make sure we weren't getting contamination. I haven't seen the truck since.

But...I have seen a ton more coming in, all for wicked misfires and all solved by replacing the upstream HO2S. The majority have been the Vin Z flex fuel motors, but a few have been regular Vin T motors as well.

So...anyone else seeing this pattern failure? I'm curious if it is a manufacturing defect or a geographic/climate issue or what. FWIW most trucks have between 50,000 and 125,000 on them and we haven't seen downstream failures even though it is the same part number as the upstream sensor until 2005.

Like anything stuff breaks and wares out. The problem is the owners! They NEVER touch the truck period. O2's and plugs are about the only thing you have to change on these motors other than oil and they fucking barely change the oil!

I would change the front 02s at every 75,000 miles. Most are never changed. I think that causes most problems other than basic shit like intake leaks, bad plugs, and such.

I think flex-fuel is a joke and GM's way of looking good on paper. I think it will cause some more misfire problems down the road or worse. But it does make more HP though!! Haha

As far as a patten I bet GM warranty could tell you!:D Fuck the trucks are made to not be touch and are pretty reliable. I people are lazy and don't take care of there shit.
They see a SES light and fucking drive it till it blows the fuck up.



For the noted problems there are MILLIONS of 5.3ls that have been made and I heard few problems on those that are cared for.


EDIT: On the flex fuel motors are they running E85 or are the just failing on gas? And don't the earlier flex fuel trucks use a fuel comp sensor. I know with the Gen IV they did away with them.

Some have been caused by faulty injector plugs. Actually just went through this with a '00 that I bought.

EDIT: On the flex fuel motors are they running E85 or are the just failing on gas? And don't the earlier flex fuel trucks use a fuel comp sensor. I know with the Gen IV they did away with them.

I have now asked every owner what kind of fuel they run in a quest for more information on this problem. None of them have ever run E85. All have run regular 87 octane. Of worthwhile note might be that all fuel in Minnesota is E10 other than the non-oxygenated premium which is to only be used in collector cars, small engines, yada yada yada.

I haven't had any complaints from customers on the cost. I think the Standard SG1157 lists for under $150 and the labor is pretty minimal to swap one out. Even the preferred GM parts aren't that expensive. I DO worry about future catalyst problems though. The converters for these trucks are not cheap. It's amazing how many people will drive for a long time with a flashing check engine light (catalyst damaging misfires :eek:) thinking the flashing means something minor like a loose gas cap or something. It's a fine example of RTFM. Sadly, with as smooth running as these new engines are a single misfire can be difficult to detect without a scan tool, but come on...when an entire bank is misfiring and black smoke is pouring out the exhaust?

I would agree that everything has a certain life expectancy and these things are not failing prematurely. It's just odd to see so many failing so similarly. Changing the sensors out really should be considered part of the extended normal maintenance, but in reality it isn't. People will replace them when they fail.

I would love to see some warranty data if someone has access to it. We are an independent shop so our only access to pattern failure stuff is through IATN or Identifix. I honestly haven't looked at either to see. I love both resources, but both make it too easy to just start hanging parts looking for a silver bullet. Sure, I've done it (blower control modules on later W-bodies when the fan stays on with the key out for example), but that's usually when I'm at the end of the road.

I really do like the LS based engines and there really haven't been any problems with them that we've seen. Heck, even the intake gaskets seem immune to the effects of old, contaminated Dex-Cool. Maybe that's what strikes me as so odd about these failures.

Well...it happened again today

2004 1/2 ton Suburban, 5.3 Vin Z w/ throttle by wire, always run on regular E10 87 octane for it's 55,000 mile life.

The lady was smart and came in right away before any real damage took place, but once again there were a bunch of P030x codes, but no P113x codes. A quick look at the datastream on the Genisys confirmed it...35mV on B2S1, STFT in the 50-60 range and LTFT at 25% and climbing.

I threw in a Bosch O2 sensor (one pledged to a different customer with the same problem!) and immediately the STFT and LTFT dropped down and the misfires cleared up as the raw fuel in the cylinders was burned off. Yet another one fixed.

Now here's something interesting. The lead time is getting longer and longer on replacement O2 sensors. The dealerships are having a hard time getting them. I can get the Bosch sensors from Carquest overnight, but haven't had great luck with them. Even more interesting is that SMP lists a supercession in J-Con, but doesn't give any more detail than saying the old part number has been superceded by an unknown new number.

Well...it happened again today

2004 1/2 ton Suburban, 5.3 Vin Z w/ throttle by wire, always run on regular E10 87 octane for it's 55,000 mile life.

The lady was smart and came in right away before any real damage took place, but once again there were a bunch of P030x codes, but no P113x codes. A quick look at the datastream on the Genisys confirmed it...35mV on B2S1, STFT in the 50-60 range and LTFT at 25% and climbing.

I threw in a Bosch O2 sensor (one pledged to a different customer with the same problem!) and immediately the STFT and LTFT dropped down and the misfires cleared up as the raw fuel in the cylinders was burned off. Yet another one fixed.

Now here's something interesting. The lead time is getting longer and longer on replacement O2 sensors. The dealerships are having a hard time getting them. I can get the Bosch sensors from Carquest overnight, but haven't had great luck with them. Even more interesting is that SMP lists a supercession in J-Con, but doesn't give any more detail than saying the old part number has been superceded by an unknown new number.Shit O2's maybe? That strange. Most places have E10. Somethings fucking the O2's up.

Might be a GMP!
Guaranteed Maintenance Program! Lol :D





Seems to me like I have heard of some O2 prolems before on later engines even flex fuel ones. I'll have to see if I can find something about them.

i can't say ive seen an extrodinary number of O2s for these trucks fly off the shelves here. Yeah, ive sold a few, but dont see the epidemic yet here...We sell a few of them, but its not one of the more notable things like triton coils or GM 3.1-3.8 intake sets...

I have an 02 z code 5.3 transplant in my trail rig...and i must say, everything seems to have failed with it...lol. Bad IAC right now, along with FPR...and 90K miles on the motor. Had a bad coolant temp sensor and/or pigtail as well...but so far, the 02s are ok.

My 03 5.3 truck was missing under power, idling bad and sometime shutting off at idle. I took apart and cleaned the throttle body out with carb cleaner and mass air sensor. There was a bunch of carbon and tar stuff in it from the EGR? It seems to run better now. I also had the cats plug up too and trough codes after i fix that no more miss fire codes.

Were your misfire codes random though? I'm talking misfires up an entire bank (P0301, P0303, P0305, P0307 and a P0300 for good measure). Often time the O2 will be fine at idle and seem to switch ok, but as soon as you load it it smacks dead lean and drowns the entire bank in fuel. It really is interesting to watch. What kills me is that the CCM doesn't catch it and revert to open loop/base fueling to save the cats.

I haven't seen these things flying off the shelf like the V-6 intake sets either, but I find it so interesting that we've seen so many of them lately with such similar characteristics (age, mileage, etc) failing on what have been otherwise rock solid reliable trucks. I think we've done more 5.3 O2 sensors than Ford coils in the last 2 months. :eek:

I'm going to do some more research on the part number for those O2's. I know they are the same for both banks both upstream and downstream until 2004. In 2005 the downstreams changed. I also know that a 2002 Vin T upstream is not the same as the ones we're seeing the failures on though they look identical and plug in just fine.

I want to see what other products use this particular sensor...

yeah we've been doing quite a few at the shop I work at, a co worker thinks it has something to do with the sensors location in the exhaust system, I just do oil changes and other bitch work so I don't have the full story but I do know we've been doing a few, with similar mileages and years to what you describe, however nothing like 3.1/3.4 intake gaskets, haha, nothing will match that, except maybe 3800 plenums...

holy shit! just realized you live in Eveleth, I work at Ken's A-1 in Hibbing, maybe it does have something to do with the climate?...

I replaced the downstream one on the left bank of the wifes Suburban. 2000 5.3 with 162,000 miles. Never had any trouble with upstream ones. Hers has got a little miss at idle, I have to check TPS range and clean the throttle body, then see what happens. Most people do not do much to these trucks, its the curse of reliability I guess. Seems like most people think the blinking SEL is not as serious as a steady burning one, it even says so in the owners manual.
Then of course everyone thinks the smog stuff is all covered for 7 years (it actually is in California) so they just drive it. Once I retire I am going to devote some time to learning more about this stuff. Maybe it does have something to do with that ass biting cold weather you guys have been having. Condensation forming in the exhaust manifolds and exposing the sensors to water on start up? Who the hell knows, but if you figure it out let us know. Good luck.

holy shit! just realized you live in Eveleth, I work at Ken's A-1 in Hibbing, maybe it does have something to do with the climate?...

Hmmm...well now we have confirmation within the same geographic area. Maybe we can just blame it on that shitty gas coming from the Murphy refinery in Superior...

Have the service manager get in touch with GM Service Research in Warren Michigan. They are involved with issues just like this. My guess is a change in PCM cal. Likely a wider parameter.

Second would be Powertrain Division at the GM tech Center. 313-556-5000.

Have the service manager get in touch with GM Service Research in Warren Michigan. They are involved with issues just like this. My guess is a change in PCM cal. Likely a wider parameter.

Second would be Powertrain Division at the GM tech Center. 313-556-5000.

But that would be stealing money out of my pocket! :laughing: I work for an independent shop and these are GRAVY jobs now that we know all the signs and the fix.

All the kidding aside though I WOULD like to hear from someone involved with GM. All these vehicles have been out of warranty and some of the GM techs I've talked to said they haven't seen it in warranty. Their shop rates are so high that they don't see a lot of vehicles out of warranty except for the Cadillacs and Buicks belonging to the old folks.

We don't do PCM reflashes. We don't have the capability at our shop, nor do we want the responsibility. Independent shops are great at what they do, but there are certain things better left to the guys the eat, sleep, and breath GM and have factory support at their hands. I am curious how a PCM reflash would change this though? I can see a flash maybe making the CCM more aware that the O2 values aren't switching and forcing it to a base fuel map, but I'm not sure that there is a parameter that will make these things not fail unless there is something going on with our fuel quality.

The days are finally starting to get a little longer now. I wonder if summer blend fuel will show a decline in these problems.

Had another one today. 2003 Tahoe, Z-code 5.3, 67,000 miles. P0300 (misfires) and P0171 (Bank 1 lean). B1S1 laid flat at 0 volts, LTFT was skyrocketing, and the cat was glowing orange as the misfire counters just kept racking them up. Swapped in a new sensor and road tested it to clear it out and get the LTFT back into a normal range and all was well. Yet another $221 half hour fix.

Yet another $221 half hour fix.
You are the devil!:D

You are the devil!:D

Now in my defense that includes the parts price (and appropriate mark up :flipoff2:) but I think that's a realistic price. There was the initial hook up and scan which I've seen shops charge a half hour labor for. There was the replacement of the part. Then there was further driving the verify the repair, get the fuel trims back in check, and check the ABS. I don't think 1.5 hours of labor is an unfair rate and probably falls in line with book time, give or take. That leaves $107 for a 4 wire oxygen sensor which doesn't amount to a huge mark up. I don't feel guilty taking advantage of knowing this problem and beating the clock because there are plenty of times I get my ass KICKED on book time (not that we are a flat rate shop, per say).

have you checked tsb's lately?

Bulletin 05-06-04-029 deals with these exact symptoms, but refers to using E85 fuel in these engines and doesn't cover the 2005's we've seen. The bulletin basically says that the gaskets take a shit when excess fuel from higher flow (i.e. under E85 operation) erodes them. None of the vehicles we have had ever ran more than the state mandated E10 ethanol concentration. We have smoked a few of the trucks that came in with this problem and have seen no vacuum leaks.

There are no TSB's I've found (identifix lists 1031 for this engine family :eek:) that deal with the specific problem of upstream O2's of this particular part number taking a dive. There may well be a reflash for the PCM out that could cure this problem, but I haven't heard of it and we don't do reflashes yet (independent shop). So far replacing the sensors has proven to be the fix although we have had shitty luck with the Bosch sensors from Carquest coming back (2 out of 3 I believe). The SMP sensor have done ok for us, and of course, the AC Delco parts work great, but are cost prohibitive in many cases.

My 03 5.3 truck was missing under power, idling bad and sometime shutting off at idle. I took apart and cleaned the throttle body out with carb cleaner and mass air sensor. There was a bunch of carbon and tar stuff in it from the EGR? It seems to run better now. I also had the cats plug up too and trough codes after i fix that no more miss fire codes.

just so you know you just fucked your Tbody, and your MAF, Never use carb cleaner to clean those parts. there are coatings on the Tbody and the MAF is a sensor not a good idea. They make chemicals to clean those parts for a reason. Oh they mite not fail right away but they will fail, they always do.

Good shit for cleaning all kinds of parts...

http://edge.shop.com/ccimg.shop.com/220000/227900/227917/products/-!CRC%20Mass%20Air%20Flow%20Sensor%20Cleaner%2011%2 0oz%20--26984633.jpg

I work for a GMC dealership, and your right i hardly ever see non warrt. work anymore. Shit has fallen off bad, and its gettin worse. I have not seen many bad O2s in my neck of the woods. but i have seen more recently, just have four bad ones on a 00 R motor today, the two downstreams had bad heaters (which is what usually happens to them) and the two upstreams were just junk. the cust. was complaining of no power on hills, and a SES light, vhl had codes for all the Os and lean conditions on both backs. what happens is the comp sees the O2s go out and then it trys to richen or lean out the mixture, causing the engine to either lean missfire or richen it up so much it will almost stall out. Out this way i see a lot of O2s in trailblazers in the 4.2 always the upstream ones. so it mite be the O2s but i think it mite have to do with the shitty gas they are selling the stuff out here smells like it has been sitting for years. We dont have any E85 out here by the way.

It doesn't surprise me that the dealerships haven't seen these trucks come in given that they have all had about 60-80,000 miles and a couple years on them putting them outside of warranty. I doubt O2's fall under any sort of emissions warranty.

I haven't seen a Trailblazer yet, interestingly enough. I know out gas in this area is pretty inconsistent, but it all comes (essentially) from one refinery.

The new vehicles are too damn smart. They just keep right on compensating for "going lean" and dumping fuel in until the damn thing is flooding itself at idle. It's a blessing and a curse I guess.

I do wonder if our E10 has a high enough alcohol content to send the trucks into a higher fuel calibration. I don't have anything to compare them to unfortunately, but I don't see the LTFT's going more than a few percent away from 0 on trucks that are running well. Of course I haven't seen anywhere on the Tech II that tells you if you're in a straight gasoline fuel map cell or an ethanol-rich cell. Our Tech II is pretty out of date though...hard to say (it does pick up on the throttle by wire stuff though...).

get friendly with someone at a GM dealership and have them update it for you, wont cost them anything and it only takes a few mins, not a huge deal.

Is it that easy to update the OTC Flash Tech II though? I was under the impression that we would need to get new cards...

We just got a Genisys 3.0 Evo with the smart cable. It's a cool scan tool in that it communicates with 98% of the vehicles that we get through our doors, but DAMN is that thing slow. I don't feel guilty charging people half an hour to scan their cars with that thing because it takes it so damn long to acquire data in the datastream. There is honestly about a 3 second delay between the upstream O's switching from lean to rich on that thing.

The Tech II is still easily my favorite scan tool. I even use the 3 in 1 software of Global OBD II when I can get away with it. A Chrysler DRBIII is pretty cool too, but we can't justify buying one when the majority of the vehicles we get through the door are still GM products.

Long live the Tech II. :laughing:

i've personally seen 2 catalyst failures on the 5.3's one was an 01 with oil consumption problems and the other was an 03 suffered bad compression in cylinder 5 after the cats went bad. My assumption was a faulty O2/rich condition

IIRC there was a TSB for rough running engine, random misfires on one bank, and the fix was to relace the front O2 sensor, i did 1 before and fixed it, just my .02