O2 sensor error

mbalbritton

mbalbritton

#@$%!
Joined
Mar 22, 2005
Location
Lakeland, FL
About 5-6 months ago I had a check engine light come on. Took it to the store to have them scan it. Came back with an O2 sensor error.

Went ahead and ordered all 4 O2 sensors from RockAuto. By the time they came in, the engine light had gone off. So, I stuck the sensors on the shelf and waited.

FFWD to the other day and the light is on again. I ordered one of those Bluetooth OBD2 scanners and it’s reading the following:
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It’s all bank 1 sensor 1.

What’s the chances I have a bad new sensor? What’s the chances it’s something else?
 
What vehicle are we dealing with here? What brand of replacement O2 sensors did you get?
 
Oh ya…

2014 GMC Sierra 5.3

I’ll have to go back and see if the O2 brand is in my RockAuto history.

EDIT: Went back and found that I ordered them from Amazon. Reluctantly admit that it looks like I ordered some China brand.

Might be worth looking at replacing bank 1 sensor 1 with a better brand and see what happens.
 
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What @Croatan_Kid said. O2 sensors are one of those where the parts house just doesn’t cut it and you don’t get to skimp. Chased my ass for a long time and fires the parts cannon at a Jeep once. OEM O2 sensor and magically all my problems were solved.
 
I usually go for Denso or NTK when it comes to O2 sensors. They make a lot of factory ones anyway. It's possible the ones you got aren't up to snuff, but make sure every fuses in that thing is good. Idk if they still do it, but in days past, the O2 sensor heater ciruit drew power through the same circuitry as other, completely unrelated stuff. As did the power for the OBDII port, which was usually the 12v outlet.

Looks like the upstream/sensor 1 sensors are the same left to right. Same for downstream/sensor 2.

Denso brand are 40 bucks a piece for the upstream ones on RockAuto 👌

With the code going from low voltage to high voltage on the heater circuit, it sorta makes me lean towards that sensor itself having a bad heating element.
 
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Croatan_Kid said:
I usually go for Denso or NTK when it comes to O2 sensors. They make a lot of factory ones anyway. It's possible the ones you got aren't up to snuff, but make sure every fuses in that thing is good. Idk if they still do it, but in days past, the O2 sensor heater ciruit drew power through the same circuitry as other, completely unrelated stuff. As did the power for the OBDII port, which was usually the 12v outlet.

Looks like the upstream/sensor 1 sensors are the same left to right. Same for downstream/sensor 2.

Denso brand are 40 bucks a piece for the upstream ones on RockAuto 👌

With the code going from low voltage to high voltage on the heater circuit, it sorta makes me lean towards that sensor itself having a bad heating element.
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Checked all fuses on all three panels. Under hood, and on end of dash in door jam on both sides. I only know of those three, if there’s more. All fuses gave me a continuity beep or passed visual inspection. Guess it’s O2 replacement time.
 
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You can download Torque app and use with the BT dongle. It an chart the 02 voltage. Once the engine has run a while, if you see a change in the O2 output, the heater is likely bad, as @Croatan_Kid mentioned.
 
ordered 4 new Denso sensors from Rock Auto. Swapped them out. Cleared everything with the scanner and took it for a ride. Maybe it was my imagination, but it seems to idle smoother. I had noticed recently a little rougher idle than normal, but felt good today.

Driving normal and watching the Scanner O2 readings for voltage and mixture (or whatever it was, not that I know what those numbers should be) They were at least registering and both banks reading the same. I got on the throttle pretty hard, and just like magic that stupid engine shaped light on the cluster illuminated. MOTHER $#%#$@%!!!

Ran a scan and got the same O2 sensor codes as previous, but also got a new one: P0420 Catalyst system.

Truck has 175K on it, just FYI. It's been a great truck. Only ever had to replace both AC lines and a temp sensor. excluding battery, tires, filters and brakes of course.
 
And it’s back like a bad case of crabs… or so I’ve heard.

Now that im spending some time to understand the numbers and readings… looks like the down stream sensors aren’t reading short term fuel trim. Might be the cheapy reader I have. I watched while driving around and they never registered at all.
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Sounds like the cats could be due for replacement.

Provided there's no issues with any injectors, fuel pressure, or intake gaskets...that may be the culprit.
 
doing some reading around online, Fuel filter could be an issue, which reminded me of a fuel tank pressure switch that I replaced 5-6 months ago.

I've never replaced the injectors. or had any work done on the engine. I certainly hope it's not the cats. Odd that it started as all bank one and now after swapping sensors, its both banks and the Cat system errors for both banks. I'm inclined to replace the filter to start with. far cheaper than cats and hasn't ever been replaced that I know of, so it couldn't hurt. REALLY don't want it to be the cats!!
 
mbalbritton said:
doing some reading around online, Fuel filter could be an issue, which reminded me of a fuel tank pressure switch that I replaced 5-6 months ago.

I've never replaced the injectors. or had any work done on the engine. I certainly hope it's not the cats. Odd that it started as all bank one and now after swapping sensors, its both banks and the Cat system errors for both banks. I'm inclined to replace the filter to start with. far cheaper than cats and hasn't ever been replaced that I know of, so it couldn't hurt. REALLY don't want it to be the cats!!
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COOL! I found the Fuel Filter right between the Blinker Fluid and Muffler Bearings. Apparently there is NO fucking serviceable Fuel filter on this truck.

If it is the Cats, Guess I need to figure out WHY.

please don't be the cats...

This modern computerised bullshit is annoying.
 
Yep...the last GM, half ton trucks with external fuel filters were the 99-02s. In 2003, they ditched the fuel filters AND cabin air filters. Terrible ideas...

Anyway, I'm leaning towards the cats at this point. If they're shot, it's either from a lean or rich condition that either cooked the inside or washed them out.

With all that said, I'd definitely confirm before replacing the cats. I'm not super familiar with the newer trucks with direct injection. I do, at least, know that low fuel pressure can cause spray pattern issues (as could partially stopped up injectors) and the AFM/DOD can have issues that would throw raw fuel in the exhaust.

I'd guess further diagnostic work would be in order!

It also wouldn't hurt to put some miles on it and *clean* the exhaust out. By that, I mean with the skinny pedal :D

Edit: Also...if you haven't done them lately...plugs and wires! Start simple.
 
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mbalbritton said:
COOL! I found the Fuel Filter right between the Blinker Fluid and Muffler Bearings. Apparently there is NO fucking serviceable Fuel filter on this truck.

If it is the Cats, Guess I need to figure out WHY.

please don't be the cats...

This modern computerised bullshit is annoying.
Click to expand...
Pm me the tag number and codes. I will send you oem testing
 
OK, so Noel has been helping me on the side in PMs. We've narrowed it down to most likely being the Cats. Since my last PM to him, I have a little more insight as I learn more about what I'm looking at on the Scanner readings.

What's happened since this thread:
Swapped to GM Genuine O2 sensors. That cleared up some of the code, but things were still acting funky.
I ran everything that I've done by him, including my suspicions of my T-Stat. I have felt that my operating temps were too low according to the dash gauge. It has been reading in the 175-185 range. According to the live data on the scanner, I was running 165-173.
Swapped the T-Stat and now temps are 195-205 on the scanner and 210 on the gauge.
Some codes are gone now, but I'm still left with the 420/430 codes that point towards the cat.

New news from my crash course education:
Watching the voltage on the Up stream and down stream sensors, all 4 are fluctuating from .07-.845.

Now that I understand that the upstream should fluctuate as the system leans and enriches the mixture, but the downstream SHOULD NOT fluctuate if the Cats are doing their job. We are both pretty suspect of the cooler running temps having some portion of blame on clogging the cats. That and 177K miles. So , keep an eye on your temp!!!

So, it looks like the Cats are not working. I'm going to try a bottle of the CatClean just to see, but I doubt it will do anything for the long haul. Looks like some new exhaust parts are in my future.

Thanks @Noel for the help!
 
sooooooo. Kinda interesting. Bought a $26 bottle of Catclean, dumped it into a 1/4 tank of gas and drive about 15 minutes around town.

I have readings from earlier today at temp and ideling in the drive way. I took 8 random screenshots over about 30 seconds. Then I did it again after the 15 minutes drive with Catclean. Here are the results.

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The down stream readings really smoothed out! I actually find it hard to believe that this actually did clean. I can only say that the readings are better. and yes I double checked the decimal placements. I'll keep an eye on it and see. I want to fill the tank now and run it before clearing the codes.
 
Makes sense. Those trucks are notorious for thermostats and temp sensors. The fuel system won't act right if it isn't getting up to temp, so I can believe it!

It'd be awesome if a bottle or two of cleaner got them back functional.
 
If the cats are clogged the exhaust at the tailpipe is way hotter than usual. A basic hand test at the tailpipe will give you an idea if it is.
 
FYI, no dice on the Catclean as halfway suspected and halfway hoped.

While the numbers on the data stream still look better, Check engine keeps coming back with same 0420- 0430 codes. Guess I'm still looking at the inevitable replacement of the Cats in order to properly fix this.

Looks like not too difficult of a swap. luckily someone engineered this section to bolt in and can be done in the driveway. What i'm wondering now is, what quality do I need to run with? They really range in price and I only want to do this once.


Rock Auto:
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