How Many Oxygen Sensors In An 04?

[MikeInCtown]

04 Sierra 5.3 engine. I think it may be running a bit rich and since it has 103k on it I figured I may look at new oxy sensors. On my older trucks there were 3 or 4. I know there are upstream and downstream listed ,but is it just one up and one down, or two up and one down?

 

 

(oddly enough this happened after new plugs and wires, but even a second set of wires didn't change anything and the plugs all look the same with none in any different shape, so I'm thinking something that would account for an across the board mixture change may be the culprit.)

[VR021302]

should be 4, 2 before and 2 after the cats

[danthaman1980]

04 Sierra 5.3 engine. I think it may be running a bit rich and since it has 103k on it I figured I may look at new oxy sensors. On my older trucks there were 3 or 4. I know there are upstream and downstream listed ,but is it just one up and one down, or two up and one down?

 

 

(oddly enough this happened after new plugs and wires, but even a second set of wires didn't change anything and the plugs all look the same with none in any different shape, so I'm thinking something that would account for an across the board mixture change may be the culprit.)

 

My 2003 has 4 oxygen sensors - 2 upstream and 2 downstream. I have heard that the upstream O2 sensors are the ones the ECM uses to monitor oxygen levels and adjust the fuel/air ratio accordingly. The downstream sensors apparently are there just to monitor the performance of the catalytic converters.

 

Before you fork over the dough for new O2 sensors though, you may want to make sure the new plugs aren't the culprit. What type of plugs did you switch over to? I've seen similar problems on GMs when trying to use different types of spark plugs. (For example, GMs don't typically like Autolites... My brother once included a set of 8 Autolites in a tune up, and the engine ran pig rich until he went back to AC Delco plugs.) From my experience, the 1999+ GM trucks like the stock AC Delcos and NGK V-Power spark plugs the best.

[MikeInCtown]

OE number A/C plugs were used. As soon as I changed them i noticed a mileage drop on the DIC hen on the highway, as much as 3 or 4 mpg at any given time. When I usd to go up a hill on cruise I would see 17-18mpg and now I'm doing 14-15. Even the flats don't net me as much as I would show 21-23@65 I now show 20-21 and that's with the wind helping me out.

 

I would try new plugs but at $50 a set I'm just not sure. After I changed them I found that within 500 miles the bottom of the plugs where the thread seats are were already covered in black carbon where the old ones were pure clean. I went so far as to even buy an extra set of A/C wires and change out the brand new ones I had gotten. I notice now that I have a slightly choppy idle at times. Not rough, but you could tell that maybe it didn't fire at exactly the right time or that it didn't get the exact right amount of fuel. Not setting any codes.

 

Perhaps a good injector cleaning is in order? It just seems odd that all this started when I changed the plugs and wires.

[Draenor]

Were the gaps in the plugs checked?

 

*edit* If you were running rich, pull the plugs and inspect them.

[MikeInCtown]

Pulled one plug tonight and it looks just like it did the last time I looked ~1,500miles ago. Only this time the tip of the plug (arm that extends from threaded area and sits furthest into the cylinder -can't remember for the life of me) was a slight grayish color that was nearing =what I saw on the old plugs. The porcelain part was still bright white. Carbon deposits were still on the threaded portion that extended into the chamber. Did not smell strongly of fuel but did have slight smell. Nothing big though. Would think 2,000 miles would be enough for a computer to adapt, but I've heard of people saying that their mileage kept rising as they piled the miles on. Got 3k miles on the oil right now and will probably change this weekend. May help a little.

[jwalker]

To further this thread, I have the same situation. Same truck, year, etc. 5.3 with VIN of T for the engine code. I need the AC Delco part number for the O2 sensors for before the cats. The Dealer here is a little hesitant on getting me the info.

[txab]

To further this thread, I have the same situation. Same truck, year, etc. 5.3 with VIN of T for the engine code. I need the AC Delco part number for the O2 sensors for before the cats. The Dealer here is a little hesitant on getting me the info.

Denso was installed as OE 2344668. All 4 O2 sensors are the same

 

ACD 2131702

[jwalker]

Ok so I see that there's different O2 sensors, heated & non heated, broadband etc. What is the best? Confusing.

 

Also, do you normally change all 4 at the same time?

[txab]

Why are you changing?

[jwalker]

100,000 maint. No codes but im a pro-active person & I dont like to wait till problems occour. Plus, I read on these forums that O2's usually get lazy or fail after 100k.

[txab]

Running crap gas is hard on them. We've got trucks with over 175k and they read and perform the same as new. Ever looked at live data from them to see how they are performing?

[jwalker]

I will be on April 4th at the Black Bear tuning event in Chicago.

[txab]

Just replace the upstream O2s for now, if you're changing them. Then the downstream if they give you code problems