I bought some Bosch o2's and they suck! They come off and on at any given moment. I need to fix this problem...any suggestions?

 

What Bosch sensors did you buy & are you using extensions? I'm running the Bosch 13111's which are the Vette rears. They have a longer harness which deletes the extension for stock O2's to reach LT collectors. They also have a slightly different element & are supposed to be more accurate when used in our cars as a front set of O2's.

I have read some cars are weird about what brand of sensor they respond to though. Have you checked the voltage at the harness plug? Do they come on/off randomly or after hitting a bump? It could be several different things.

 

We've experienced the same thing with brand new Bosch and other aftermarket o2 sensors. This is why we only run and only recommend AC Delco OE replacement sensors from GM. They really are a better sensor, in my opinion!

 

What do you mean by "come on and off at any given moment"?

Have you put a scope on the O2 sensors to see what kind of voltage they're putting out? Is the voltage switching b/w about 0.1v-0.9v? Is the SES light on? Did you scan for DTCs? Are you sure there isn't an open circuit or intermittently bad connector somewhere between the PCM and the O2 sensors? If they're brand new sensors and they're cutting out, I'd inspect the car a little more closely before condemning a new part.

Easiest thing to do? Return them to the auto part store for another pair, and swap in the newer O2 sensors. If they cure the problem? Voila. Then you can say Bosch sucks. But until we get more info, let's withhold a little judgement.

 

I have read that that Denso's are a better choice, read:
http://www.camarohomepage.com/project/part3.htm


bottom is Denso

 

Hmm, my car is loving the Bosch 13111's. From everything I have seen the Denso is identical to what GM offers as the Delco stock replacement sensor but the dealer charges more. I have also seen plenty of the sensors be hit or miss. Its a crap shoot really.

Like stated, check all connections & voltage. If everything check out then return the sensors for another set & if that fixes it then you will know 100% it was just the sensors.

 

One minute they read correctly and the next they are not. Usually happens when it's either really hot and cold. Any other time they're fine.

 

It's not a crap shoot. Here's why.

I'm seriously suggesting you use OEM sensors. I'm telling you from experience that this is one place not to play around - the car relies on these for fuel delivery. Is that really where you want to cut corners? The sensors that came with the car are exactly what the PCM was designed to read. Any other sensor substitute will never be better for the engine than OEM sensors that the engineers at GM spec'd for the car. Using other brands risks all sorts of driveability glitches for the rest of the life of the car.

The reason for OEM vs. aftermarket sensor differences is that there are all sorts of tolerance specifications for the manufacture of these sensors. As long as the sensor is manufactured within those tolerances, it's considered safe for use on the car. Is it safe? Technically, yes. But the tolerances to which it was made are almost always much wider than OEM requirements, which is how they make the sensors cheaper. They scrimp. Cut corners. OEM is manufactured to much tighter tolerances than aftermarket sensors, that's why they cost more (they want your car to work perfectly the day you drive it off the lot!). Better manufacturing means they read more accurately than aftermarket sensors. You get what you pay for.

Other sensors leave more room for wiggle, but not O2 sensors. They are critical sensors and should be original equipment - every time you replace them.

'Nuff said. That's up to each car's owner. YCYDYP.

Most O2 sensors generate their own electrical signal, as do the O2s used in G4 F-bodies. If your new O2s are intermittently generating, that means they're putting out a signal but it's not always making it to the PCM (also depends on where you put the leads for your scope to watch the signal, too). If you checked the voltage range, and when working, it's correct, then the only other area for a problem to exist is either with the (A) wiring/connectors or (B) the PCM.

Have you double checked with a scanner to make sure no codes are present? It would be odd, but there's a chance your MIL indicator simply isn't lighting.

I ask because normally, your problem should cause a DTC due to sensor voltage reading problems, but one never knows. Your PCM may have a problem, and might not be reading the sensors correctly. I always suspect modules last, because it's almost always a wire, connector or sensor that fails before a module takes a poop.

This suggests an intermittent open circuit to the O2 sensors that's not remaining open long enough to set a code. Break out your DMM, find a circuit diagram to trace so you know what you're testing, and start tracing the circuit until you find the problem.

Good luck. LUK.

 

I'd disagree. And GM did not engineer the oxygen sensor, at least not to my knowledge anyway. Thats just the sensor they picked for this vechicle application. Many many many people have switched to the Bosch 13111's (which are the Vette rear O2 sensors) for the front O2's b/c they come with a longer harness out of the box & eliminate the need to a extension which is just another area for potiential failure. They also heat more easily which is what you want when you have LT's. Many people who have made the switch to the 13111's have had good results & some of them report better A/F ratios. In the end fact remains not all sensors are created equal.

Just b/c a sensor is a stock OEM component doesnt mean if you replace it with another brand it wont work right & could kill your engine. Thats almost a laughable concept honestly. Fact remains it is a crap shoot, period. If it wasnt then there wouldnt be as many options & everyone would only run OEM pieces. But obviously thats not the case at all. Some cars like the Bosch sensors & respond to them, likewise with the NGK, Denso, AC Delco & so fourth.

My car is running strong & perfectly fine on my brand new 13111's so how can that be if only the stock units operate correctly?

 

Another thing GM points out in their technotes: a dropped O2 Sensor is a BAD O2 Sensor...

 

No, they didn't - you're right. I misspoke on that count. What they did do was engineer the PCM circuits around the chosen OEM provider's specs, which are very frequently of a higher grade than aftermarket replacements. Not always, but usually.

I'm both an engineer and an experienced dealer tech. I'm giving you an engineer's point of view... but more so a technician's standpoint. My job as a dealer technician is to keep cars running as trouble-free and as long as possible between maintenances. I frequently see my brand's performance V8 products in our garage, often being cured of problems caused by less expensive non-OEM parts. As I said previously, there are many sensors that don't matter whether you buy them from Autozone or get bent over at the dealer, but there are others that are better purchased OEM. In my experience and opinion, an OEM O2 sensor is a better bet than an aftermarket.

YCYDYP = your car, your dough, your prerogative. I'm running OEM sensors in Grotyohann 1-7/8 LT's on my setup. The car ran a best of 11.88 making 441hp/421tq. I'm sure there are a zillion guys out there running way better and faster than I am on aftermarket O2's. No need to get anyone's panties in a wad. I'm just saying from a reliability and performance standpoint, I'm an OEM guy when it comes to this subject.

Never said it would kill the engine. I said it could cause problems, particularly with driveability. I say this because I've personally replaced aftermarket sensors with OEMs at work before, and seen that cure driveability concerns immediately. I'd be happy to cite the cases that come to mind if you PM me.

Ciao for now...

-R

 

I understand what you are saying, but you are over-thinking that just a tad. An OEM narrowband O2 sensor is not rocket science by any means, its primitive at best. A 20+ year old design on production vehicles. To say a "pcm is designed around this specific sensor and won't work adequately with any other sensor" is hogwash.

 

I see where your coming from Bluestreak, but that just proves my point. And yours to a certain extent. You proved what I say is correct, not all cars like all brands of sensors. So you replaced aftermarket with stock & it cured problems. Obviously for some reason those cars were picky about the sensor they would operate properly with. But we all know not every car responds identically.

This has always been a area of bewilderment for me, you would think all the PCM's would be identical coming from the dealer on say all 99' model Fbody cars. Yet some respond to parts better than others & some like you stated only run at their full potiential with OEM parts. I have always wondered why this is & how it can even be, but havent wondered enough to read the mountain of data on why, LOL.

 

I'v had the bosch 13111's and they sucked, scaning with HPT the 13111's would barely switch. I switched to denso's and tons of problems went away. Just my experience!

 

It's a problem getting any O2 to work right w/LT's b/c they mount further downstream where the exhaust is cool, giving a false reading and setting off codes. OEM's have seemed to work best in my experience, but any of them can be problematic when installed in LT's.