Slowboy

Looking to replace all my O2 sensors on my 2008 Chevy Silverado 1500 5.3 L. It is equipped with a Magnuson Supercharger. I asked Summit about O2 Sensors they recommend and they referred me to Delphi brand. I need to know if I can buy all the same or if the upstream are different from the downstream? As far as I know I have two upstream and two downstream. I have a true dual exhaust. Delphi seems like real durable sensors which is what I am looking for since I have a boosted vehicle. I need to get these replaced and have it mixing the air to fuel ratio right and have it running strong again. Please help.

tech2

I can't answer your question. I believe them to be the same but I'm not a parts guy. The only difference I wonder about is the length of the wiring from sensor to connector.


the front 2 are used for the fuel metering. the rears are not. So if your are just having a fuel metering problem, leave the post cat 02's alone.

country_09

Upstream and downstream have different plug ends, one is male and one is female, but as said above you only need the front 2 of upstream sensors to be able to adjust for fuel/air needs. The 2 downstream ones can be tuned out or you can leave them alone. Most people run Longtube headers and tune the rear o2 sensors out. Both my trucks are like that

Slowboy

I do have long tube headers. And my downstream O2 sensors are before the cats which I know isn't correct. What do you mean by tune the 2 downstream out? You mean by having it programmed to be mapped out? I guess I never really thought about that as a possibility or it might already be like that. I am getting a Lean Bank 1 and 2 engine code assciated with my CEL along with Heater Sensor Core. I can't remember the details on them but they are ALL associated with my O2 sensors.

I was also told to weld another female thread on top of the other O2 sensor collar on the exhaust for both upstream sensors that way it backs it out of the way from the exhaust a little and still adjusts the fuel mixture well and makes the sensor last longer and work better.

Thanks for all the info keep the opinions and help coming.

tech2

Lean don't don't necessarily mean the 02 are bad. they could be correctly reading a lean condition. lean fuel trim codes can be caused by bad maf, low fuel pressure, vacuum leaks and bad 02. it rare that both 02 would go bad at the same time.


To weld a bung on the 02 sensor fitting sounds like bad advice.


what have you done to the fuel system to compensate for the added fuel demand of a boosted truck?

Slowboy

Well it us worth replacing them because the truck has 106K miles on it now. Chances are they are bad from what I was told especially with a boosted vehicle giving off a lot of exhaust heat. As far as I know I don't have any vacuum leaks. I do not know what my fuel pressure is or what a good pressure would be but I imagine that the person who put the supercharger on it had to upgrade the pump. Wouldn't I also be getting a code if I had a bad MAF sensor? My codes are all O2 sensor related and that is what three mechanics told me. It has been a problem that got worse with time. When I first bought it with 40K it ran great.

tech2

Put your 02 in then and see what happens. If it doesn't fix it, find out the codes and post them.


lean fuel trim codes can set from a bad maf with no other maf sensor codes setting. the hot wire becomes contaminated and skews the sensor reading. the readings are incorrect but do not fail other logic tests that are used to determine out of spec parameters. people running junk cai with poor quality or oiled filters kill maf sensors.
Modified or poorly designed induction systems can also be the cause of false lean dtc. With your aftermarket system the custom tune should account for that




get it fixed soon. boosted engines don't like running lean.

country_09

You have longtubes and cats? Not many people do that. And yeah you just delete the rear o2 sensors essentially. Only the upstream ones are needed. Do you have all 4 sensors before the cats? Doesn't sound right

Slowboy

Thanks for the input. I am learning as I go with this truck. I will start off by replacing the O2 sensors and see what happens. Then go from there. That was my plan. Just wanted to get further info from others to see what other possibilities it could be.

Yes I have long tube headers with a true dual exhaust that has cats. And all 4 sensors are before the cats. Everyone wonders why they put them like that. I think they got lazy and just put them there to make it easy.

tech2

makes no sense; the entire purpose of the rear o2 is to monitor the condition of the cat. putting the rear sensors pre cat would set cat efficiency codes. Since your not getting these codes, your custom tune has deleted the monitor for the cats.