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Check Engine Light (Both Upstream 02 sensors)

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My 2014 3.7L literally has 452 miles beyond the 100k warranty....and the check engine light comes on.

 

I stopped an Advance Auto and they read the code as both upstream 02 sensors (guy didn't tell me the PO).  

 

I was just under the car last weekend for an oil change and while I didn't examine the harness, I saw nothing awry.  

 

New sensors are $130 each from Advance.  

 

I was going to check the harness and connections tomorrow, than order if they look intact.

 

On the 2nd restart, the light went out.

 

I think it is odd that both 02 sensors would throw a code at the same time?   That leads me to believe it's not each sensor going bad.

 

My last two cars had 800k on them (03 & 08) and I sold them with the original 02 sensor, so to me, this seems odd.

 

Also of late, my MPG has INCREASED by 1.5 or so (as you probably deduced, I drive a lot, so the increase was notable to me).  The car was purchase in 2016 with 14k  on it.

 

I know we have some technicians here and wondered what they thought about this situation.  

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Don't shoot the messenger. The O2 sensors are telling you there is a problem, which is why they are there. Upstream O2 sensors detect the amount of harmful emissions going into the catalytic converter. If they detect a problem, it's probably time for a tune-up. It's hard to tell by just knowing the fault code exactly what the problem is. A good technician will check active engine monitors and long and short term fuel trim to help pin-point the exact parts to remove and check for wear or malfunction. He may also check the voltage to the sensors themselves to make sure the proper voltage switching is occuring.

Long story short, Advanced Auto cannot even begin to steer you in the right direction.

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Thanks Medium, I understand how the work.   I had a ODBII code reader/programmer for my laptop, but I haven't had a code for 15 years, so i ditched the laptop last year.

I just wondered if it was odd to get a code on both banks.  The code went out and hasn't returned (likely it will). Wish I still had my reader, which showed pending codes, and of course the code itself. 

But, without the FSM, it's kind of spitting into the dark. 

I was hoping a tech might chime in and see if this was a reocurring program. 

Has anyone replaced an 02 sensor on a 2014?  Guessing I'm the high mileage guy on that powertrain?

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Dag. That's cold. I'm a tech. I don't think you know how they work based on your explanation of the problem. Good luck

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I appreciate your input.

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Without knowing the codes, there's no surefire way to diagnose this, especially over the Internet.  I'd take MediumWilly's advice and don't just start throwing parts at it based on what the parts-counter guy says. 

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Guys, I need to apologize for the way I came off.  I clearly didn't word my request correctly.

 

I completely realize that the chance that both 02 sensors went bad simultaneously is slim to none.    I had no intention of throwing away $225 on new 02 sensors. 

 

 I have well over 1 million miles in  three, modern-era  vehicles with zero 02 sensor failures (which were pretty common in the 90's).

 

So, I was just wondering what the instance here was of 02 failure and it there was any pattern on the 3.7L motor.

 

If someone replied that "we replace them routinely", that would give me consideration to think about replacing them.

 

Having said all that, the car continues to show no more codes.

 

I'm crawling under it now, to check the wires and connectors.  You may remember that I had an ice jam under the under-tray back in January.  I gave the underneath a cursory examination back then and didn't see anything amiss.

 

Thanks for sticking with me and I apologize if I came off like an ass-hat, I can communicate better than that.

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Well, there is definitely no wire tears or issues with the connections.

 

Curiously, on the right bank sensor, the three wires an 1" from the sensor has a small zip tie.  The other side does not.  I wonder if someone did have some issues? (that doesn't strike me as factory).

 

Still no CEL.  I'll run it up to Advance again and see if there are any pending codes (hoping their reader will see that?). 

 

I wish that I hadn't ditched my old OBD program, but it was in a very old laptop and used a printer port connect for the OBD II connection (to the laptop).  No new laptops have those type of ports. (but it did still boot up fine).  Lesson learned. 

I know that these programs are on phone app's now.  I'll have to investigate that option. (or love feedback from users).

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With both banks throwing codes, it has to be something in common with all cylinders, i.e. air intake or overall fuel pressure. CEL codes don't always point directly to the culprit. If you don't have a code reader with sensor monitors, you can check your O2 sensors by putting a multi-meter on them with the engine running. The voltage should be continuously variable. This is what techs call "voltage switching". If the voltage is a constant value or none, replace that 02 sensor. There is also a range that the voltage should switch between which will vary by vehicle. If it is out-of-range, that denotes a problem with the internal combustion process. This shows that the sensor is doing its job by detecting inefficient combustion. More diagnosis is required. There is a common misconception about how these things work. Your average auto tech may not even know this. Scary. That's why no one touches my car except me.

Downstream 02 sensors work in the same fashion, except an out-of-range condition points to a bad catalyst process.

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Thanks Willy.  I miss my old OBD-2 program, that had several 02 sensor monitoring features.

I'll had Advance again tomorrow, ran out of time this evening.

 

I did happen to clean and re-oil my Green air filter last weekend ,and wondered if that wasn't the issue.  (I was pretty careful to not over-oil, but who knows).  I usually clean the TB and MAF on those task but didn't last weekend, I hope that didn't bite me (well, that would be an easy fix).  I bought the Green precisely because of all the MAF issues being reported lately with K&N filters.  I've used a K&N in all my vehicles since the early 90's without any issues, perhaps I should have stuck with them...

 

More to come!

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I've had the K&N installed for years with nothing to report except better performance. Too much air cleaner oil will definitely trip a sensor as that oil is vacuumed into the combustion chamber.

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Well, I've put on about 700 miles since last weekend.  

The CEL has not returned.

On Sunday, I cleaned the MAF and throttle body.  I typically do this when the air-cleaner is cleaned and re-oiled, but did not in this instance.

I guess I'll find out if the I solved the problem, or just delayed it.

 

Thanks for all of the input, it's great to have input from pro technicians.

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Thanks Willy.  I miss my old OBD-2 program, that had several 02 sensor monitoring features.

I'll had Advance again tomorrow, ran out of time this evening.

 

I did happen to clean and re-oil my Green air filter last weekend ,and wondered if that wasn't the issue.  (I was pretty careful to not over-oil, but who knows).  I usually clean the TB and MAF on those task but didn't last weekend, I hope that didn't bite me (well, that would be an easy fix).  I bought the Green precisely because of all the MAF issues being reported lately with K&N filters.  I've used a K&N in all my vehicles since the early 90's without any issues, perhaps I should have stuck with them...

 

More to come!

upstream, both air sensors, I was going to say bad gas but clearing quickly said no. The air filter did it. I'm saying.

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upstream, both air sensors, I was going to say bad gas but clearing quickly said no. The air filter did it. I'm saying.

 

And I bought the Green because of the recent issues reported with K&N's.  I've used K&N drop-in and CAI's for over 20 years, with zero MAF/CEL issues, I should have stuck with them.

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